Multi-chamber rotary piston actuator

ABSTRACT

The subject matter of this specification can be embodied in, among other things, a fluid actuator including a housing defining a first chamber having a first cavity and a first open end, a first piston assembly including a tubular first piston defining a second chamber having a second cavity and a second open end, disposed in said first housing for reciprocal movement in the first chamber through the first open end, wherein a first seal, the first cavity, and the first piston define a first pressure chamber, and a second piston assembly having an second piston disposed in said first piston assembly for reciprocal movement in the second chamber through the second open end, wherein a second seal, the second cavity, and the second piston define a second pressure chamber, and a first portion of the second piston contacts a first end effector.

CROSS REFERENCE TO RELATED APPLICATIONS(S)

This application claims the benefit of priority to U.S ProvisionalPatnet Application Ser. No. 62/371,317, filed Aug. 5, 2016 and U.S.Provisional Patent Application Ser. No. 62/449,879, filed Jan. 24, 2017,the contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to an actuator device and more particularly to arotary piston type actuator device wherein the pistons of the rotor aremoved by fluid under pressure.

BACKGROUND

Linear hydraulic actuators of various forms are currently used inindustrial mechanical power conversion applications. One commonindustrial usage is in construction equipment (e.g., excavators,backhoes) in which the linear action of a hydraulic piston is convertedto rotary motion about a joint.

In certain applications, such as the actuators used for heavy equipmentoperation, increased actuation speed, wide ranges of motion, efficiencyof fluid power usage, and ease of maintenance are desired. However,despite their widespread use, it can be difficult to provide suchcharacteristics in typical heavy equipment applications of linearhydraulic actuators, e.g., on the arm and bucket of an excavator.

Rotary hydraulic actuators of various forms are also currently used inother types of industrial mechanical power conversion applications. Thisindustrial usage is commonly for applications where continuous inertialloading is desired without the need for load holding for long durations,e.g., aircraft using rotary vane actuators on flight control surfaces,and applications where load holding is not an issue, e.g., backhoesusing hydraulic motors to pivot the house or boom horizontally relativeto the undercarriage. The designs of such actuators, however, do notscale well to provide the combinations of power-to-weight ratios,field-serviceability features, stiffnesses, holding capacities,torque-to-weight ratios, slew rates, energy efficiency, and/or thefield-serviceability typically expected by heavy equipment operators foruse elsewhere in their equipment, e.g., actuation of vertical joints ofthe arm.

SUMMARY

In general, this document relates to rotary piston-type actuators.

In a first aspect, a rotary piston actuator assembly comprises a firstrotary actuator comprising a first housing defining a first arcuatechamber comprising a first cavity having a first open end, and anarcuate-shaped first piston disposed in said first housing forreciprocal movement in the first arcuate chamber through the first openend, and a first arcuate bearing sleeve assembly having an inner surfaceconfigured to be contacted by a radially outer side of the first piston.

In a second aspect, according the aspect one, the first arcuate bearingsleeve comprises an arcuate support portion and an arcuate liner portionconfigured to conform to an inner surface of the arcuate supportportion.

In a third aspect, according to aspect one or two, the first arcuatebearing sleeve assembly is removably affixed to the first housing.

In a fourth aspect, according to any one of aspects one to three, thefirst rotary actuator further comprises a rotor assembly rotatablysurrounding said first housing and defining a first central bore withinan inner wall of the rotor assembly, and wherein the first arcuatebearing sleeve assembly is arranged radially between the first pistonand the inner wall, and in contact with the radially outer side of thefirst piston and the inner wall.

In a fifth aspect, according to aspect four, the first arcuate bearingsleeve assembly is arranged radially between the first piston and theinner wall, in contact with the radially outer side of the first pistonand the inner wall.

In a sixth aspect, according to aspect four or five, the rotary actuatorfurther comprises a fluid delivery shaft having an elongated body, thefluid delivery shaft being disposed in a second central bore defined bythe first housing and in fluid communication with the first cavity.

In a seventh aspect, according to any one of aspects four to six, therotor assembly further comprises a rotary output tube about the axis anda rotor arm in contact with a first portion of the first piston, saidrotor arm extending radially outward to the rotary output tube andcoupled to the rotary output tube.

In an eighth aspect, according to any one of aspects four to seven, therotary actuator further comprises a second rotary actuator disposedwithin the first central bore.

In a ninth aspect, according to aspect eight, the second rotary actuatorfurther comprises a second housing defining a second arcuate chambercomprising a second cavity having a second open end, and anarcuate-shaped second piston disposed in said second housing forreciprocal movement in the second arcuate chamber through the secondopen end.

In a tenth aspect, according to aspect nine, the rotary actuator furthercomprises a second arcuate bearing sleeve assembly, arranged radiallybetween the second piston and the inner wall, in contact with a radiallyouter side of the second piston and the inner wall.

In an eleventh aspect, according to any one of aspects one to ten, thefirst arcuate bearing sleeve comprises a collection of bearings.

In a twelfth aspect, according to any one of aspects one to eleven, thefirst arcuate bearing sleeve comprises a friction-reducing coating.

In a thirteenth aspect, a method of rotary actuation comprises providinga first rotary actuator comprising a first housing defining firstarcuate chamber comprising a first cavity having a first open end, andan arcuate-shaped first piston disposed in said first housing forreciprocal movement in the first arcuate chamber through the first openend, wherein a first seal, the first cavity, and the first piston definea first pressure chamber comprising part or all of the first arcuatechamber, and a first arcuate bearing sleeve assembly having an innersurface configured to be contacted by a radially outer side of the firstpiston, urging the first piston partially rotationally outward from thefirst pressure chamber, and applying, by the first arcuate bearingsleeve portion, a first radial force to the radially outer side of thepiston.

In a fourteenth aspect, according to aspect thirteen, the method furthercomprises urging the first piston partially radially outward, contactingthe first piston to the first arcuate bearing sleeve assembly with asecond radial force, transmitting the second radial force to the firsthousing, and constraining, by first arcuate bearing sleeve assembly, thesecond radial force.

In a fifteenth aspect, according to aspects thirteen or fourteen, themethod further comprises providing a second rotary actuator, wherein therotor assembly rotatably surrounds the first rotary actuator and thesecond rotary actuator.

In a sixteenth aspect, according to any one of aspects thirteen tofifteen, the method further comprises redirecting the first radial forcethrough the first arcuate bearing sleeve assembly to a rotor assemblyrotatably surrounding said first housing and defining a central borewithin an inner wall of the rotor assembly, wherein the first arcuatebearing sleeve assembly is removably affixed to the first housing.

In a seventeenth aspect, according to any one of aspects thirteen tosixteen, the method further comprising redirecting the first radialforce through the first arcuate bearing sleeve assembly to the firsthousing, wherein the first arcuate bearing sleeve assembly is removablyaffixed to the first housing.

In a eighteenth aspect, according to any one of aspects thirteen toseventeen, applying, by the first arcuate bearing sleeve portion, afirst radial force to the radially outer side of the piston furthercomprises applying the first radial force to a collection of bearings incontact with the radially outer side of the piston.

In a nineteenth aspect, according to any one of aspects thirteen toeighteen, the first arcuate bearing sleeve portion comprises afriction-reducing coating, and wherein applying, by the first arcuatebearing sleeve portion, a first radial force to the radially outer sideof the piston further comprises applying the first radial force to thefriction-reducing coating in contact with the radially outer side of thepiston.

In a twentieth aspect, a fluid actuator comprising a housing defining afirst chamber comprising a first cavity, a first fluid port in fluidcommunication with the first cavity, and a first open end, a firstpiston assembly comprising a tubular first piston defining a secondchamber comprising a second cavity, a second fluid port in fluidcommunication with the second cavity, and a second open end, disposed insaid first housing for reciprocal movement in the first chamber throughthe first open end, wherein a first seal, the first cavity, and thefirst piston define a first pressure chamber, and a second pistonassembly comprising an second piston disposed in said first pistonassembly for reciprocal movement in the second chamber through thesecond open end, wherein a second seal, the second cavity, and thesecond piston define a second pressure chamber, and a first portion ofthe second piston contacts a first end effector.

In a twenty-first aspect, according to aspect twenty, the first chamberis an arcuate first chamber comprising the first open end and a firstenclosed end, the tubular first piston is an arcuate-shaped tubularfirst piston, the second chamber is an arcuate second chamber comprisingthe second open end and a second enclosed end, the second piston is anarcuate-shaped second piston, and the end effector is a rotor arm.

In a twenty-second aspect, according to aspect twenty or twenty-one, thehousing further defines a third arcuate chamber comprising a thirdcavity, a third fluid port in fluid communication with the third cavity,and a third open end, the first piston assembly further comprises anarcuate-shaped tubular third piston defining a fourth arcuate chambercomprising a fourth cavity, a fourth fluid port in fluid communicationwith the fourth cavity, and a fourth open end, disposed in said firsthousing for reciprocal movement in the third arcuate chamber through thethird open end, wherein a third seal, the third cavity, and the thirdpiston define a third pressure chamber, and the second piston assemblyfurther comprises an arcuate-shaped fourth piston disposed in said firstpiston assembly for reciprocal movement in the fourth arcuate chamberthrough the fourth open end, wherein a fourth seal, the fourth cavity,and the fourth piston define a fourth pressure chamber, and a firstportion of the fourth piston contacts a second end effector.

In a twenty-third aspect, according to aspect twenty-two, the fluidactuator further comprises a rotor arm, wherein the first chamber is anarcuate first chamber, the tubular first piston is an arcuate-shapedtubular first piston, the second chamber is an arcuate second chamber,the second piston is an arcuate-shaped second piston, the third chamberis an arcuate third chamber, the tubular third piston is anarcuate-shaped tubular third piston, the fourth chamber is an arcuatefourth chamber, the fourth piston is an arcuate-shaped fourth piston,the first end effector is the rotor arm, and the second end effector isthe rotor arm.

In a twenty-fourth aspect, according to aspect twenty-three, the secondpiston is oriented in the same rotational direction as the first piston.

In a twenty-fifth aspect, according to aspect twenty-three, the secondpiston is oriented in the opposite rotational direction as the firstpiston.

In a twenty-sixth aspect, according to aspect twenty-three, applicationof pressurized fluid to the third pressure chamber urges the thirdpiston partially outward from the third pressure chamber to urgerotation of the first piston assembly in a first direction, applicationof pressurized fluid to the fourth pressure chamber urges the fourthpiston partially outward from the fourth pressure chamber to urgerotation of the second piston assembly in the first direction, rotationof the second piston assembly in a second direction opposite that of thefirst direction urges the fourth piston partially into the fourthpressure chamber to urge pressurized fluid out the fourth fluid port,and rotation of the first piston assembly in the second direction urgesthe third piston partially into the third pressure chamber to urgepressurized fluid out the third fluid port.

In a twenty-seventh aspect, according to any one of aspects twenty-oneto twenty-six, the housing further defines an arcuate actuation spacedefining an actuation arc about the axis between the first open end anda terminal end, and the fluid actuator further comprises a rotorassembly comprising a rotary output tube rotatably surrounding saidhousing, wherein the rotor arm extends radially outward to the rotaryoutput tube and the rotor arm is coupled to the rotary tube.

In a twenty-eighth aspect, according to any one of aspects twenty-one totwenty-seven, the first seal is disposed about an interior surface ofthe first open end.

In a twenty-ninth aspect, according to any one of aspects twenty-one totwenty-eight, the first seal is disposed about the periphery of thefirst piston and is configured to remain stationary relative to thefirst piston.

In a thirtieth aspect, according to any one of aspects twenty-one totwenty-nine, the second seal is disposed about an interior surface ofthe second open end.

In a thirty-first aspect, according to any one of aspects twenty-one tothirty, the second seal is disposed about the periphery of the secondpiston and is configured to remain stationary relative to the secondpiston.

In a thirty-second aspect, according to any one of aspects twenty-one tothirty-one, the housing is formed as a one-piece housing.

In a thirty-third aspect, according to any one of aspects twenty-one tothirty-two, the first piston has one of a square, rectangular, ovoid,elliptical, figure-eight, or circular shape in cross-section.

In a thirty-fourth aspect, according to any one of aspects twenty-one tothirty-three, the first piston assembly further defines a fluid portfluidically connecting the first cavity and the second cavity.

In a thirty-fifth aspect, according to any one of aspects twenty-one tothirty-four, a first portion of the tubular first piston contacts asecond end effector.

In a thirty-sixth aspect, a method of fluid actuation comprisesproviding a fluid actuator comprising a housing defining a first chambercomprising a first cavity, a first fluid port in fluid communicationwith the first cavity, and a first open end, a first piston assemblycomprising a tubular first piston defining a second chamber comprising asecond cavity, a second fluid port in fluid communication with thesecond cavity, and a second open end, disposed in said first housing forreciprocal movement in the first chamber through the first open end,wherein a first seal, the first cavity, and the first piston define afirst pressure chamber, and a second piston assembly comprising ansecond piston disposed in said first piston assembly for reciprocalmovement in the second chamber through the second open end, wherein asecond seal, the second cavity, and the second piston define a secondpressure chamber, and a first portion of the second piston contacts afirst end effector, applying pressurized fluid to the first pressurechamber, urging the first piston partially outward from the firstpressure chamber to urge the end effector in a first direction, urgingthe end effector in a second direction opposite that of the firstdirection, urging the first piston partially into the first pressurechamber to urge pressurized fluid out the first fluid port, applyingpressurized fluid to the second pressure chamber, urging the secondpiston partially outward from the second pressure chamber to urge thefirst piston assembly in the first direction, urging the first pistonassembly in the second direction, and urging the second piston partiallyinto the second pressure chamber to urge pressurized fluid out thesecond fluid port.

In a thirty-seventh aspect, according to aspect thirty-six, the firstchamber is an arcuate first chamber comprising the first open end and afirst enclosed end, the tubular first piston is an arcuate-shapedtubular first piston, the second chamber is an arcuate second chambercomprising the second open end and a second enclosed end, the secondpiston is an arcuate-shaped second piston, the end effector is a rotorarm, urging the first piston partially outward from the first pressurechamber to urge the end effector in a first direction further comprisesrotating the rotor arm in the first direction with substantiallyconstant torque over stroke, and urging the second piston partiallyoutward from the second pressure chamber to urge the first pistonassembly in the first direction further comprises rotating the firstpiston assembly in the first direction with substantially constanttorque over stroke.

In a thirty-eighth aspect, an arm of a machine apparatus comprises afirst arm portion, a second arm portion, and a joint portion connectingthe first arm portion to the second arm portion, the joint portioncomprising a fluid actuator comprising, a housing defining a firstchamber comprising a first cavity, a first fluid port in fluidcommunication with the first cavity, and a first open end, a firstpiston assembly comprising a tubular first piston defining a secondchamber comprising a second cavity, a second fluid port in fluidcommunication with the second cavity, and a second open end, disposed insaid first housing for reciprocal movement in the first chamber throughthe first open end, wherein a first seal, the first cavity, and thefirst piston define a first pressure chamber, and a second pistonassembly comprising an second piston disposed in said first pistonassembly for reciprocal movement in the second chamber through thesecond open end, wherein a second seal, the second cavity, and thesecond piston define a second pressure chamber, and a first portion ofthe second piston contacts a first end effector.

In a thirty-ninth aspect, according to aspect thirty-eight, the endeffector is affixed to or is integral to the first arm portion.

In a fortieth aspect, according to aspect thirty-eight or thirty-nine,the housing is affixed to or is integral to the second arm portion.

In a forty-first aspect, multi-axis rotary actuator comprises a firstrotary piston actuator configured to controllably actuate a firstpivotal joint between a first linkage to a second linkage about a firstaxis, and a second rotary piston actuator configured to controllablyactuate a second pivotal joint connecting the second linkage to a thirdlinkage about a second axis.

In a forty-second aspect, according to aspect forty-one, the first axisis parallel to the second axis.

In a forty-third aspect, according to aspect forty-one, the first axisis perpendicular to the second axis.

In a forty-fourth aspect, according to aspect forty-one, the first axisintersects the second axis.

In a forty-fifth aspect, according to any one of aspects forty-one toforty-four, at least one of the first rotary piston actuator and thesecond rotary piston actuator comprises a housing defining a firstarcuate chamber comprising a first cavity defining a first arc in aplane between a first open end and a first enclosed end and having afirst fluid port in fluid communication with the first cavity, the firstarc having a first radius in the plane, the first radius defining anaxis perpendicular to the plane, and an arcuate actuation space definingan actuation arc about the axis between the first open end and aterminal end, a rotor arm configured for rotary movement within theactuation space along a second arc, an arcuate-shaped first pistondisposed in said housing for reciprocal movement in the first arcuatechamber and in the plane through the first open end, wherein a firstseal, the first cavity, and the first piston define a first pressurechamber comprising part or all of the first arcuate chamber, and a firstportion of the first piston contacts the rotor arm, and a rotor assemblyrotatably surrounding said housing and comprising a rotary cylinderabout the axis, wherein the rotor arm extends radially outward to therotary cylinder and the rotor arm is coupled to the rotary cylinder,wherein the housing is coupled to a selected one of the first linkage,the second linkage, or the third linkage, and the rotor assembly iscoupled to another one of the first linkage, the second linkage, or thethird linkage.

In a forty-sixth aspect, according to aspect forty-five, the multi-axisrotary actuator further comprises a second arcuate chamber comprising asecond cavity defining a second arc about the axis between a second openend and a second enclosed end and having a second fluid port in fluidcommunication with the second cavity.

In a forty-seventh aspect, according to aspect forty-six, the second archas a second radius from the axis, different from the first radius.

In a forty-eighth aspect, according to aspect forty-seven, the secondarc is concentric with the first arc about the axis in the plane.

In a forty-ninth aspect, according to aspect forty-eight, the secondopen end is at the terminal end, and the arcuate chamber is orientedrotationally opposite to the first arcuate chamber about the axis.

In a fiftieth aspect, according to aspect forty-eight, the second arc isnot in the plane and at least a portion of the second arcuate chamberoverlaps axially with the first arcuate chamber in the plane.

In a fifty-first aspect, according to aspect forty-eight, the multi-axisrotary actuator further comprises an arcuate-shaped second pistondisposed in said second housing for reciprocal movement in the secondarcuate chamber through the second open end, wherein a second seal, thesecond cavity, and the second piston define a second pressure chambercomprising part or all of the second arcuate chamber, and a secondportion of the second piston contacts the rotor arm.

In a fifty-second aspect, according to any one of aspects forty-five tofifty-one, the rotor assembly provides load bearing support for thehousing.

In a fifty-third aspect, according to any one of aspects forty-five tofifty-two, at least one of the first rotary piston actuator and thesecond rotary piston actuator comprises a housing defining a firstarcuate chamber housing defining a first arcuate chamber comprising afirst cavity defining a first ring segment in a plane between a firstopen end and a first enclosed end and having a first fluid port in fluidcommunication with the first cavity, the ring segment having a firstouter radius in the plane, the first radius defining an axisperpendicular to the plane, a first inner radius in the plane, and afirst central radius in the plane, a second arcuate chamber comprisingan inner chamber wall defining a second cavity defining a second ringsegment in the plane between a second open end and a second enclosed endand having a second fluid port in fluid communication with the secondcavity, the second ring segment having a second outer radius from theaxis, larger than the first outer radius and concentric with the firstouter radius about the axis in the plane, a second inner radius smallerthan the first inner radius in the plane, and a second central radiussubstantially the same as the first central radius, wherein the secondarcuate chamber is oriented rotationally opposite to the first arcuatechamber about the axis and wherein at least a portion of the firstarcuate chamber housing is enclosed within at least a portion of thesecond arcuate chamber in the plane and defining an arcuate tubularspace between the first arcuate chamber housing and the inner chamberwall, and an arcuate actuation space defining a third arc in the planeabout the axis between the first open end and the second open end, arotor arm configured for rotary movement within the actuation spacealong the third arc, a rotor assembly coupled to the rotor arm, anarcuate-shaped first piston disposed in said first housing forreciprocal movement in the first arcuate chamber and in the planethrough the first open end, wherein a first seal, the first cavity, andthe first piston define a first pressure chamber, and a first portion ofthe first piston contacts a rotor arm, and a tubular, arcuate-shapedsecond piston disposed in said second housing for reciprocal movement inthe second arcuate chamber, in the arcuate tubular space and in theplane through the second open end, wherein a second seal, a third seal,the second cavity, and the second piston define a second pressurechamber, and a second portion of the second piston contacts the rotorarm, wherein the housing is coupled to a selected one of the firstlinkage, the second linkage, or the third linkage, and the rotorassembly is coupled to another one of the first linkage, the secondlinkage, or the third linkage.

In a fifty-fourth aspect, a method of multi-axis rotary actuationcomprises providing a multi-axis rotary actuator comprising a firstrotary piston actuator configured to controllably actuate a firstpivotal joint between a first linkage to a second linkage about a firstaxis, and a second rotary piston actuator configured to controllablyactuate a second pivotal joint connecting the second linkage to a thirdlinkage about a second axis, applying pressurized fluid to the firstrotary piston actuator, urging actuation of the first pivotal jointabout the first axis in a first direction, urging actuation of the firstpivotal joint about the first axis in a second direction opposite thatof the first direction, applying pressurized fluid to the second rotarypiston actuator, urging actuation of the second pivotal joint about thesecond axis in a third direction, and urging actuation of the secondpivotal joint about the second axis in a fourth direction opposite thatof the third direction.

In a fifty-fifth aspect, according to aspect fifty-four, applyingpressurized fluid to the first rotary piston actuator further comprisesapplying pressurized fluid to a first pressure chamber of the firstrotary piston actuator configured to urge actuation of the first pivotaljoint in the first direction, and wherein applying pressurized fluid tothe second rotary piston actuator further comprises applying pressurizedfluid to a third pressure chamber of the second rotary piston actuatorconfigured to urge actuation of the second pivotal joint in the thirddirection, and the method further comprises applying pressurized fluidto a second pressure chamber of the first rotary piston actuatorconfigured to urge actuation of the first pivotal joint in the seconddirection, urging actuation of the first pivotal joint about the firstaxis in the second direction, applying pressurized fluid to a fourthpressure chamber of the second rotary piston actuator configured to urgeactuation of the first pivotal joint in the second direction, and urgingactuation of the second pivotal joint about the second axis in thefourth direction.

In a fifty-sixth aspect, an arm of a machine apparatus comprises a firstarm portion, a second arm portion, and a joint portion pivotallyconnecting the first arm portion to the second arm portion, the jointportion comprising a multi-axis rotary actuator comprising a firstrotary piston actuator configured to controllably actuate a firstpivotal joint between a first linkage to a second linkage about a firstaxis, and a second rotary piston actuator configured to controllablyactuate a second pivotal joint connecting the second linkage to a thirdlinkage about a second axis.

In a fifty-seventh aspect, according to aspect fifty-six, the first axisis parallel to the second axis.

In a fifty-eighth aspect, according to aspect fifty-six, the first axisis perpendicular to the second axis.

In a fifty-ninth aspect, according to aspect fifty-six, the first axisintersects the second axis.

In a sixtieth aspect, according to any one of aspects fifty-six tofifty-nine, at least one of the first rotary piston actuator and thesecond rotary piston actuator comprises a housing defining a firstarcuate chamber comprising a first cavity defining a first arc in aplane between a first open end and a first enclosed end and having afirst fluid port in fluid communication with the first cavity, the firstarc having a first radius in the plane, the first radius defining anaxis perpendicular to the plane, and an arcuate actuation space definingan actuation arc about the axis between the first open end and aterminal end, a rotor arm configured for rotary movement within theactuation space along a second arc, an arcuate-shaped first pistondisposed in said housing for reciprocal movement in the first arcuatechamber and in the plane through the first open end, wherein a firstseal, the first cavity, and the first piston define a first pressurechamber comprising part or all of the first arcuate chamber, and a firstportion of the first piston contacts the rotor arm, and a rotor assemblyrotatably surrounding said housing and comprising a rotary cylinderabout the axis, wherein the rotor arm extends radially outward to therotary cylinder and the rotor arm is coupled to the rotary cylinder,wherein the housing is coupled to a selected one of the first linkage,the second linkage, or the third linkage, and the rotor assembly iscoupled to another one of the first linkage, the second linkage, or thethird linkage.

In a sixty-first aspect, a rotary piston actuator assembly comprises afirst rotary actuator comprising a first housing defining a firstcentral bore, and a first arcuate chamber comprising a first cavityhaving a first actuator fluid port in fluid communication with the firstcavity and the first central bore, a rotor arm, an arcuate-shaped firstpiston disposed in said first housing for reciprocal movement in thefirst housing, wherein a first seal, the first cavity, and the firstpiston define a first pressure chamber comprising part or all of thefirst arcuate chamber, and a first portion of the first piston contactsthe rotor arm, a rotor assembly rotatably surrounding said first housingand comprising a rotary output tube, wherein the rotor arm extendsradially outward to the rotary output tube and the rotor arm is coupledto the rotary tube, and a fluid delivery shaft having an elongated bodydisposed in said first central bore and defining a first shaft fluiddelivery path.

In a sixty-second aspect, according to aspect sixty-one, the rotarypiston actuator assembly further comprises a second rotary actuatorcomprising a second housing defining a second central bore, a secondarcuate chamber comprising a second cavity having a second actuatorfluid port in fluid communication with the second cavity and the secondcentral bore, and an arcuate-shaped second piston disposed in saidsecond housing for reciprocal movement in the second housing, wherein asecond seal, the second cavity, and the second piston define a secondpressure chamber comprising part or all of the second arcuate chamber,and a first portion of the second piston contacts the rotor arm, whereinthe rotor assembly rotatably surrounds said second housing, and thefluid delivery shaft is disposed in said second central bore.

In a sixty-third aspect, according to aspect sixty-one or sixty-two, thefluid delivery shaft defines an axis and comprises a first shaft fluidport along the body, a second shaft fluid port near a terminal end ofthe body, and the first shaft fluid delivery path defined by the fluiddelivery shaft and fluidly connecting the first shaft fluid port to thesecond shaft fluid port, a first shaft seal disposed about the fluiddelivery shaft on a first axial side of the first shaft fluid port alongthe axis, a second shaft seal disposed about the fluid delivery shaft ona second axial side of the first shaft fluid port along the axis andopposite the first shaft seal, wherein the first central bore, the body,the first shaft fluid seal, and the second shaft fluid seal define afirst fluid transmission chamber, and the first actuator fluid port isin fluidic communication with the first fluid transmission chamber.

In a sixty-fourth aspect, according to aspect sixty-three, the firstcentral bore further defines a first bore portion and a second boreportion, wherein the first bore portion extends along substantially afirst half of the axial length of the first central bore, and the secondbore portion extends along substantially the second half of the axiallength of the first central bore, and the first actuator fluid port isdefined within the first bore portion, wherein the first fluidtransmission chamber extends along substantially one half of the axiallength of the first central bore such that the first fluid transmissionchamber extends along the first bore portion in a first assemblage ofthe first rotary actuator and the fluid delivery shaft, and the firstfluid transmission chamber extends along the second bore portion in asecond assemblage of the first rotary actuator and the fluid deliveryshaft.

In a sixty-fifth aspect, according to any one of aspects sixty-one tosixty-four, the first arcuate chamber further defines a first open end,and the first piston further comprises a first piston assemblycomprising a tubular first piston defining a second chamber comprising asecond cavity, a second fluid port in fluid communication with thesecond cavity, and a second open end, disposed in said first housing forreciprocal movement in the first chamber through the first open end,wherein a first seal, the first cavity, and the first piston define afirst pressure chamber, and the rotary piston actuator further comprisesa second piston assembly comprising an second piston disposed in saidfirst piston assembly for reciprocal movement in the second chamberthrough the second open end, wherein a second seal, the second cavity,and the second piston define a second pressure chamber, and a firstportion of the second piston contacts a first end effector.

In a sixty-sixth aspect, according to any one of aspects sixty-one tosixty-five, the first cavity defines a first arc in a plane between afirst open end and a first enclosed end and having a first fluid port influid communication with the first cavity, the first arc having a firstradius in the plane, the first radius defining an axis perpendicular tothe plane, and the first housing further defines an arcuate actuationspace defining an actuation arc about the axis between the first openend and a terminal end, wherein the rotor arm is configured for rotarymovement within the actuation space along a second arc, and the firstpiston is disposed in said first housing for reciprocal movement in thefirst arcuate chamber and in the plane through the first open end,wherein the first seal, the first cavity, and the first piston definethe first pressure chamber comprising part or all of the first arcuatechamber.

In a sixty-seventh aspect, according to any one of aspects sixty-one tosixty-six, the first housing comprises a first arcuate chamber housingdefining the first arcuate chamber, wherein the first cavity defines afirst ring segment in a plane between a first open end and a firstenclosed end, the ring segment having a first outer radius in the planeand defining an axis perpendicular to the plane, a first inner radius inthe plane about the axis, and a first central radius in the plane,wherein the first housing further defines a second arcuate chambercomprising an inner chamber wall defining a second cavity defining asecond ring segment in the plane between a second open end and a secondenclosed end and having a second fluid port in fluid communication withthe second cavity, the second ring segment having a second outer radiusfrom the axis, larger than the first outer radius and concentric withthe first outer radius about the axis in the plane, a second innerradius smaller than the first inner radius in the plane, and a secondcentral radius substantially the same as the first central radius,wherein the second arcuate chamber is oriented rotationally opposite tothe first arcuate chamber about the axis and wherein at least a portionof the first arcuate chamber housing is enclosed within at least aportion of the second arcuate chamber in the plane and defining anarcuate tubular space between the first arcuate chamber housing and theinner chamber wall, and an arcuate actuation space defining a third arcin the plane about the axis between the first open end and the secondopen end, and the rotor arm is configured for rotary movement within theactuation space along the third arc, wherein the arcuate-shaped firstpiston disposed in said first housing for reciprocal movement in thefirst arcuate chamber and in the plane through the first open end,wherein the first seal, the first cavity, and the first piston definethe first pressure chamber, and wherein the rotary piston actuatorassembly further comprises a tubular, arcuate-shaped second pistondisposed in said second housing for reciprocal movement in the secondarcuate chamber, in the arcuate tubular space and in the plane throughthe second open end, wherein a second seal, a third seal, the secondcavity, and the second piston define a second pressure chamber, and asecond portion of the second piston contacts the rotor arm.

In a sixty-eighth aspect, a method of rotary actuation comprisesproviding a first rotary actuator comprising a first housing defining afirst central bore, and a first arcuate chamber comprising a firstcavity having a first actuator fluid port in fluid communication withthe first cavity and the first central bore, a rotor arm, anarcuate-shaped first piston disposed in said first housing forreciprocal movement in the first housing, wherein a first seal, thefirst cavity, and the first piston define a first pressure chambercomprising part or all of the first arcuate chamber, and a first portionof the first piston contacts the rotor arm, a rotor assembly rotatablysurrounding said first housing and comprising a rotary output tube,wherein the rotor arm extends radially outward to the rotary output tubeand the rotor arm is coupled to the rotary tube, and a fluid deliveryshaft having an elongated body disposed in said first central bore anddefining a first shaft fluid delivery path, providing pressurized fluidto the second shaft fluid port, urging pressurized fluid to the firstpressure chamber through the first shaft fluid delivery path, the firstshaft fluid port, the first fluid transmission chamber, and the firstfluid port, urging the first piston partially outward from the firstpressure chamber to urge rotation of the rotor assembly in a firstdirection, rotating the rotor assembly in a second direction oppositethat of the first direction, and urging the first piston partially intothe first pressure chamber to urge pressurized fluid out the secondshaft fluid port through the first fluid port, the first fluidtransmission chamber, the first shaft fluid port, and the first shaftfluid delivery path.

In a sixty-ninth aspect, according to aspects sixty-eight, the methodfurther comprises disassembling the first rotary actuator from a firstassembly configuration with the fluid delivery shaft, reassembling thefirst rotary actuator to the fluid delivery shaft in a secondconfiguration, providing pressurized fluid to the second shaft fluidport, urging pressurized fluid to the first pressure chamber through thefirst shaft fluid delivery path, the first shaft fluid port, the firstfluid transmission chamber, and the first fluid port, urging the firstpiston partially outward from the first pressure chamber to urgerotation of the rotor assembly in the second direction, rotating therotor assembly in the direction opposite that of the second direction,and urging the first piston partially into the first pressure chamber tourge pressurized fluid out the second shaft fluid port through the firstfluid port, the first fluid transmission chamber, the first shaft fluidport, and the first shaft fluid delivery path.

In a seventieth aspect, according to aspect sixty-eight or sixty-nine,the first central bore defines a first bore portion and a second boreportion, wherein the first bore portion extends along substantially afirst half of the axial length of the first central bore, and the secondbore portion extends along substantially the second half of the axiallength of the first central bore, and the first actuator fluid port isdefined within the first bore portion; and wherein the first fluidtransmission chamber extends along substantially one half of the axiallength of the first central bore such that the first fluid transmissionchamber extends along the first bore portion in a first assemblage ofthe first rotary actuator and the fluid delivery shaft, and the firstfluid transmission chamber extends along the second bore portion in asecond assemblage of the first rotary actuator and the fluid deliveryshaft.

In a seventy-first aspect, according to aspect seventy, the methodfurther comprises disassembling the first rotary actuator from a firstassembly configuration with the fluid delivery shaft, wherein the firstcentral bore portion, the body, the first shaft fluid seal, and thesecond shaft fluid seal define the first fluid transmission chamber inthe first configuration, reassembling the first rotary actuator to thefluid delivery shaft in a second configuration, wherein the secondcentral bore portion, the body, the first shaft fluid seal, and thesecond shaft fluid seal define the first fluid transmission chamber inthe second configuration, providing pressurized fluid to the secondshaft fluid port, and blocking flow of pressurized fluid by the firstpressure chamber.

In a seventy-second aspect, an arm of a machine apparatus comprises afirst arm portion, a second arm portion, and a joint portion pivotallyconnecting the first arm portion to the second arm portion, the jointportion comprising a first rotary actuator comprising a first housingdefining a first central bore, and a first arcuate chamber comprising afirst cavity having a first actuator fluid port in fluid communicationwith the first cavity and the first central bore, and a rotor arm, anarcuate-shaped first piston disposed in said first housing forreciprocal movement in the first housing, wherein a first seal, thefirst cavity, and the first piston define a first pressure chambercomprising part or all of the first arcuate chamber, and a first portionof the first piston contacts the rotor arm, a rotor assembly rotatablysurrounding said first housing and comprising a rotary output tube,wherein the rotor arm extends radially outward to the rotary output tubeand the rotor arm is coupled to the rotary tube, and a fluid deliveryshaft having an elongated body disposed in said first central bore anddefining a first shaft fluid delivery path.

In a seventy-third aspect, according to aspect seventy-two, the rotorassembly is affixed to or is integral to the first arm portion.

In a seventy-fourth aspect, according to aspect seventy-two orseventy-three, the housing is affixed to or is integral to the secondarm portion.

In a seventy-fifth aspect, according to any one of aspects seventy-twoto seventy-four, the arm further comprises a second rotary actuatorcomprising a second housing defining a second central bore, a secondarcuate chamber comprising a second cavity having a second actuatorfluid port in fluid communication with the second cavity and the secondcentral bore, and an arcuate-shaped second piston disposed in saidsecond housing for reciprocal movement in the second housing, wherein asecond seal, the second cavity, and the second piston define a secondpressure chamber comprising part or all of the second arcuate chamber,and a first portion of the second piston contacts the rotor arm, whereinthe rotor assembly rotatably surrounds said second housing, and thefluid delivery shaft is disposed in said second central bore.

In a seventy-sixth aspect, according to any one of aspects seventy-twoto seventy-five, the fluid delivery shaft defines an axis and comprisesa first shaft fluid port along the body, a second shaft fluid port neara terminal end of the body, and the first shaft fluid delivery pathdefined by the fluid delivery shaft and fluidly connecting the firstshaft fluid port to the second shaft fluid port, a first shaft sealdisposed about the fluid delivery shaft on a first axial side of thefirst shaft fluid port along the axis, a second shaft seal disposedabout the fluid delivery shaft on a second axial side of the first shaftfluid port along the axis and opposite the first shaft seal, wherein thefirst central bore, the body, the first shaft fluid seal, and the secondshaft fluid seal define a first fluid transmission chamber, and thefirst actuator fluid port is in fluidic communication with the firstfluid transmission chamber.

In a seventy-seventh aspect, according to aspect seventy-six, the firstcentral bore further defines a first bore portion and a second boreportion, wherein the first bore portion extends along substantially afirst half of the axial length of the first central bore, and the secondbore portion extends along substantially the second half of the axiallength of the first central bore, and the first actuator fluid port isdefined within the first bore portion, wherein the first fluidtransmission chamber extends along substantially one half of the axiallength of the first central bore such that the first fluid transmissionchamber extends along the first bore portion in a first assemblage ofthe first rotary actuator and the fluid delivery shaft, and the firstfluid transmission chamber extends along the second bore portion in asecond assemblage of the first rotary actuator and the fluid deliveryshaft.

In a seventy-eighth aspect, a rotary actuator comprises a housingdefining a first arcuate chamber housing defining a first arcuatechamber comprising a first cavity defining a first ring segment in aplane between a first open end and a first enclosed end and having afirst fluid port in fluid communication with the first cavity, the ringsegment having a first outer radius in the plane and defining an axisperpendicular to the plane, a first inner radius in the plane about theaxis, and a first central radius in the plane, a second arcuate chambercomprising an inner chamber wall defining a second cavity defining asecond ring segment in the plane between a second open end and a secondenclosed end and having a second fluid port in fluid communication withthe second cavity, the second ring segment having a second outer radiusfrom the axis, larger than the first outer radius and concentric withthe first outer radius about the axis in the plane, a second innerradius smaller than the first inner radius in the plane, and a secondcentral radius substantially the same as the first central radius,wherein the second arcuate chamber is oriented rotationally opposite tothe first arcuate chamber about the axis and wherein at least a portionof the first arcuate chamber housing is enclosed within at least aportion of the second arcuate chamber in the plane and defining anarcuate tubular space between the first arcuate chamber housing and theinner chamber wall, and an arcuate actuation space defining a third arcin the plane about the axis between the first open end and the secondopen end, a rotor arm configured for rotary movement within theactuation space along the third arc, a rotor assembly coupled to therotor arm, an arcuate-shaped first piston disposed in said first housingfor reciprocal movement in the first arcuate chamber and in the planethrough the first open end, wherein a first seal, the first cavity, andthe first piston define a first pressure chamber, and a first portion ofthe first piston contacts a rotor arm, and a tubular, arcuate-shapedsecond piston disposed in said second housing for reciprocal movement inthe second arcuate chamber, in the arcuate tubular space and in theplane through the second open end, wherein a second seal, a third seal,the second cavity, and the second piston define a second pressurechamber, and a second portion of the second piston contacts the rotorarm.

In a seventy-ninth aspect, according to aspect seventy-eight, at least aportion of the second arcuate chamber overlaps axially with the firstarcuate chamber in the plane.

In an eightieth aspect, according to aspect seventy-eight orseventy-nine, the rotor assembly is rotatably journaled in said housingand comprises a rotary output shaft along the axis, wherein the rotorarm extends radially inward to the rotary output shaft and the rotor armis coupled to the rotary output shaft.

In an eighty-first aspect, according to any one of aspects seventy-eightto eighty, the rotor assembly rotatably surrounds said housing andcomprises a rotary output cylinder about the axis, wherein the rotor armextends radially outward to the rotary output cylinder and the rotor armis coupled to the rotary output cylinder.

In an eighty-second aspect, according to any one of aspectsseventy-eight to eighty-one, the first seal is disposed about aninterior surface of the open end and is configured to remain stationaryrelative to the open end.

In an eighty-third aspect, according to any one of aspects seventy-eightto eighty-two, the first seal is disposed about the periphery of thefirst piston and is configured to remain stationary relative to thefirst portion.

In an eighty-fourth aspect, according to any one of aspectsseventy-eight to eighty-three, the first seal provides load bearingsupport for the first piston.

In an eighty-fifth aspect, according to any one of aspects seventy-eightto eighty-four, the rotor assembly provides load bearing support for thehousing.

In an eighty-sixth aspect, according to any one of aspects seventy-eightto eighty-five, the housing is formed as a one-piece housing.

In an eighty-seventh aspect, according to any one of aspectsseventy-eight to eighty-six, the first seal is a one-piece seal.

In an eighty-eighth aspect, according to any one of aspectsseventy-eight to eighty-seven, the first piston is solid incross-section.

In an eighty-ninth aspect, according to any one of aspects seventy-eightto eighty-eight, at least one of the first piston and the second pistonis at least partly hollow in cross-section.

In an ninetieth aspect, according to any one of aspects seventy-eight toeighty-nine, the first piston has one of a square, rectangular, ovoid,elliptical, figure-eight, or circular shape in cross-section.

In a ninety-first aspect, a method of rotary actuation comprisesproviding a rotary actuator comprising a housing defining a firstarcuate chamber housing defining a first arcuate chamber comprising afirst cavity defining a first ring segment in a plane between a firstopen end and a first enclosed end and having a first fluid port in fluidcommunication with the first cavity, the ring segment having a firstouter radius in the plane and defining an axis perpendicular to theplane, a first inner radius in the plane about the axis, and a firstcentral radius in the plane, a second arcuate chamber comprising aninner chamber wall defining a second cavity defining a second ringsegment in the plane between a second open end and a second enclosed endand having a second fluid port in fluid communication with the secondcavity, the second ring segment having a second outer radius from theaxis, larger than the first outer radius and concentric with the firstouter radius about the axis in the plane, a second inner radius smallerthan the first inner radius in the plane, and a second central radiussubstantially the same as the first central radius, wherein the secondarcuate chamber is oriented rotationally opposite to the first arcuatechamber about the axis and wherein at least a portion of the firstarcuate chamber housing is enclosed within at least a portion of thesecond arcuate chamber in the plane and defining an arcuate tubularspace between the first arcuate chamber housing and the inner chamberwall, and an arcuate actuation space defining a third arc in the planeabout the axis between the first open end and the second open end, arotor arm configured for rotary movement within the actuation spacealong the third arc, a rotor assembly coupled to the rotor arm, anarcuate-shaped first piston disposed in said first housing forreciprocal movement in the first arcuate chamber and in the planethrough the first open end, wherein a first seal, the first cavity, andthe first piston define a first pressure chamber, and a first portion ofthe first piston contacts a rotor arm, and a tubular, arcuate-shapedsecond piston disposed in said second housing for reciprocal movement inthe second arcuate chamber, in the arcuate tubular space and in theplane through the second open end, wherein a second seal, a third seal,the second cavity, and the second piston define a second pressurechamber, and a second portion of the second piston contacts the rotorarm, applying pressurized fluid to the first pressure chamber, urgingthe first piston partially outward from the first pressure chamber tourge movement of the rotor arm in a first direction, rotating the rotorarm in a second direction opposite that of the first direction, andurging the first piston partially into the first pressure chamber tourge pressurized fluid out the first fluid port.

In a ninety-second aspect, according to aspect ninety-one, rotating therotor arm in a second direction opposite that of the first directioncomprises applying pressurized fluid to the second pressure chamber, andurging the second piston partially outward from the second pressurechamber to urge movement of the rotor arm in a second direction oppositefrom the first direction.

In an ninety-third aspect, according to aspect ninety-one or ninety-two,urging the first piston partially outward from the first pressurechamber to urge movement of the rotor arm in a first direction furthercomprises moving the rotor arm in the first direction with substantiallyconstant torque over stroke.

In a ninety-fourth aspect, an arm of a machine apparatus comprises afirst arm portion, a second arm portion, and a joint portion pivotallyconnecting the first arm portion to the second arm portion, the jointportion comprising a rotary actuator comprising a housing defining afirst arcuate chamber housing defining a first arcuate chambercomprising a first cavity defining a first ring segment in a planebetween a first open end and a first enclosed end and having a firstfluid port in fluid communication with the first cavity, the ringsegment having a first outer radius in the plane and defining an axisperpendicular to the plane, a first inner radius in the plane about theaxis, and a first central radius in the plane, a second arcuate chambercomprising an inner chamber wall defining a second cavity defining asecond ring segment in the plane between a second open end and a secondenclosed end and having a second fluid port in fluid communication withthe second cavity, the second ring segment having a second outer radiusfrom the axis, larger than the first outer radius and concentric withthe first outer radius about the axis in the plane, a second innerradius smaller than the first inner radius in the plane, and a secondcentral radius substantially the same as the first central radius,wherein the second arcuate chamber is oriented rotationally opposite tothe first arcuate chamber about the axis and wherein at least a portionof the first arcuate chamber housing is enclosed within at least aportion of the second arcuate chamber in the plane and defining anarcuate tubular space between the first arcuate chamber housing and theinner chamber wall, and an arcuate actuation space defining a third arcin the plane about the axis between the first open end and the secondopen end, a rotor arm configured for rotary movement within theactuation space along the third arc, a rotor assembly coupled to therotor arm, an arcuate-shaped first piston disposed in said first housingfor reciprocal movement in the first arcuate chamber and in the planethrough the first open end, wherein a first seal, the first cavity, andthe first piston define a first pressure chamber, and a first portion ofthe first piston contacts a rotor arm, and a tubular, arcuate-shapedsecond piston disposed in said second housing for reciprocal movement inthe second arcuate chamber, in the arcuate tubular space and in theplane through the second open end, wherein a second seal, a third seal,the second cavity, and the second piston define a second pressurechamber, and a second portion of the second piston contacts the rotorarm.

In a ninety-fifth aspect according to aspect ninety-four, the rotorassembly is affixed to or is integral to the first arm portion.

In a ninety-sixth aspect, according to aspect ninety-four orninety-five, the housing is affixed to or is integral to the second armportion.

In a ninety-seventh aspect, a rotary actuator comprises a housingdefining a first arcuate chamber comprising a first cavity defining afirst arc in a plane between a first open end and a first enclosed endand having a first fluid port in fluid communication with the firstcavity, the first arc having a first radius in the plane, the firstradius defining an axis perpendicular to the plane, and an arcuateactuation space defining an actuation arc about the axis between thefirst open end and a terminal end, a rotor arm configured for rotarymovement within the actuation space along a second arc, anarcuate-shaped first piston disposed in said housing for reciprocalmovement in the first arcuate chamber and in the plane through the firstopen end, wherein a first seal, the first cavity, and the first pistondefine a first pressure chamber comprising part or all of the firstarcuate chamber, and a first portion of the first piston contacts therotor arm, and a rotor assembly rotatably surrounding said housing andcomprising a rotary output tube about the axis, wherein the rotor armextends radially outward to the rotary output tube and the rotor arm iscoupled to the rotary tube.

In a ninety-eighth aspect, according to aspect ninety-seven, the rotaryactuator further comprises a second arcuate chamber comprising a secondcavity defining a second arc about the axis between a second open endand a second enclosed end and having a second fluid port in fluidcommunication with the second cavity.

In a ninety-ninth aspect, according to aspect ninety-nine, the secondarc has a second radius from the axis, different than the first radius.

In a one-hundredth aspect, according to aspect ninety-nine, the secondarc is concentric with the first arc about the axis in the plane.

In a one-hundred-first aspect, according to aspect ninety-nine orone-hundred, the second open end is at the terminal end, and the arcuatechamber is oriented rotationally opposite to the first arcuate chamberabout the axis.

In a one-hundred-second aspect, according to any one of aspectsninety-nine to one-hundred-one, the second arc is not in the plane andat least a portion of the second arcuate chamber overlaps axially withthe first arcuate chamber in the plane.

In a one-hundred-third aspect, according to any one of aspectsninety-nine to one-hundred-two, the rotary actuator further comprises anarcuate-shaped second piston disposed in said second housing andconfigured for reciprocal movement in the second arcuate chamber throughthe second open end, wherein a second seal, the second cavity, and thesecond piston define a second pressure chamber comprising part or all ofthe second arcuate chamber, and a second portion of the second pistoncontacts the rotor arm.

In a one-hundred-fourth aspect, according to aspect one-hundred-three,application of pressurized fluid to the first pressure chamber urges thefirst piston partially outward from the first pressure chamber to urgerotation of the rotor arm in a first direction, and application ofpressurized fluid to the second pressure chamber urges the second pistonpartially outward from the second pressure chamber to urge rotation ofthe rotor arm in a second direction.

In a one-hundred-fifth aspect, according to aspect one-hundred-three orone-hundred-four, at least one of the first piston and the second pistoncomprises the rotor arm.

In a one-hundred-sixth aspect, according to any of aspects ninety-sevento one-hundred-five, rotation of the rotor assembly urges the firstpiston partially into the first pressure chamber to pressurize a fluidand urge the fluid out of the first fluid port.

In a one-hundred-seventh aspect, according to any of aspectsninety-seven to one-hundred-six, the rotary tube comprises the rotorarm.

In a one-hundred-eighth aspect, according to any of aspects ninety-sevento one-hundred-seven, the rotary actuator further comprises a firsthousing seal ring groove defined in the rotor assembly about the axis, asecond housing seal ring groove defined in the housing about the axisand complimentary to the first housing seal ring groove, and aring-shaped seal between the rotor assembly and the housing within thefirst housing seal ring groove and the second housing seal ring groove.

In a one-hundred-ninth aspect, a method of rotary actuation comprisesproviding a rotary actuator comprising a housing defining a firstarcuate chamber comprising a first cavity defining a first arc in aplane between a first open end and a first enclosed end and having afirst fluid port in fluid communication with the first cavity, the firstarc having a first radius in the plane, the first radius defining anaxis perpendicular to the plane, and an arcuate actuation space definingan actuation arc about the axis between the first open end and aterminal end, a rotor arm configured for rotary movement within theactuation space along a second arc, an arcuate-shaped first pistondisposed in said housing for reciprocal movement in the first arcuatechamber and in the plane through the first open end, wherein a firstseal, the first cavity, and the first piston define a first pressurechamber comprising part or all of the first arcuate chamber, and a firstportion of the first piston contacts the rotor arm, and a rotor assemblyrotatably surrounding said housing and comprising a rotary output tubeabout the axis, wherein the rotor arm extends radially outward to therotary output tube and the rotor arm is coupled to the rotary tube,applying pressurized fluid to the first pressure chamber, urging thefirst piston partially outward from the first pressure chamber to urgerotation of the rotor assembly in a first direction, rotating the rotorassembly in a second direction opposite that of the first direction, andurging the first piston partially into the first pressure chamber tourge pressurized fluid out the first fluid port.

In a one-hundred-tenth aspect, according to aspect one-hundred-nine, thehousing further defines a second arcuate chamber comprising a secondcavity defining a second arc about the axis between a second open endand a second enclosed end and having a second fluid port in fluidcommunication with the second cavity, the rotary actuator furthercomprising an arcuate-shaped second piston disposed in said firsthousing for reciprocal movement in the second arcuate chamber, wherein asecond seal, the second cavity, and the second piston define a secondpressure chamber, and a first portion of the second piston contacts thesecond rotor arm.

In a one-hundred-eleventh aspect, according to aspect one-hundred-ten,the second piston is oriented in the same rotational direction as thefirst piston.

In a one-hundred-twelfth aspect, according to aspect one-hundred-ten,the second piston is oriented in the opposite rotational direction asthe first piston.

In a one-hundred-thirteenth aspect, according to any of aspectsone-hundred-ten to one-hundred twelve, rotating the rotor assembly in asecond direction opposite that of the first direction comprises applyingpressurized fluid to the second pressure chamber, and urging the secondpiston partially outward from the second pressure chamber to urgerotation of the rotor assembly in a second direction opposite from thefirst direction.

In a one-hundred-fourteenth aspect, according to any of aspectsone-hundred-ten to one-hundred thirteen, rotating the rotor assembly ina second direction opposite that of the first direction comprisesapplying pressurized fluid to the second pressure chamber, and urgingthe first piston partially into the first pressure chamber to urgerotation of the rotor assembly in a second direction opposite from thefirst direction.

In a one-hundred-fifteenth aspect, according to any of aspectsone-hundred-nine to one-hundred-fourteen, urging the first pistonpartially outward from the first pressure chamber to urge rotation ofthe rotor assembly in a first direction further comprises rotating therotor assembly in the first direction with substantially constant torqueover stroke.

In a one-hundred-sixteenth aspect, an arm of a machine apparatuscomprises a first arm portion, a second arm portion, and a joint portionpivotally connecting the first arm portion to the second arm portion,the joint portion comprising a rotary actuator comprising a housingdefining a first arcuate chamber comprising a first cavity defining afirst arc in a plane between a first open end and a first enclosed endand having a first fluid port in fluid communication with the firstcavity, the first arc having a first radius in the plane, the firstradius defining an axis perpendicular to the plane, and an arcuateactuation space defining an actuation arc about the axis between thefirst open end and a terminal end, a rotor arm configured for rotarymovement within the actuation space along a second arc, anarcuate-shaped first piston disposed in said housing for reciprocalmovement in the first arcuate chamber and in the plane through the firstopen end, wherein a first seal, the first cavity, and the first pistondefine a first pressure chamber comprising part or all of the firstarcuate chamber, and a first portion of the first piston contacts therotor arm, and a rotor assembly rotatably surrounding said housing andcomprising a rotary output tube about the axis, wherein the rotor armextends radially outward to the rotary output tube and the rotor arm iscoupled to the rotary tube.

In a one-hundred-seventeenth aspect, according to aspectone-hundred-sixteen, the rotor assembly is affixed to or is integral tothe first arm portion.

In a one-hundred-eighteenth aspect, according to aspectone-hundred-sixteen or one-hundred-seventeen, the housing is affixed toor is integral to the second arm portion.

An rotary piston actuator assembly includes a first rotary actuatorincluding a first housing defining a first arcuate chamber including afirst cavity having a first open end, and an arcuate-shaped first pistondisposed in said first housing for reciprocal movement in the firstarcuate chamber through the first open end, and a first arcuate bearingsleeve assembly having an inner surface configured to be contacted by aradially outer side of the first piston.

Various embodiments can include some, all, or none of the followingfeatures. The first arcuate bearing sleeve can include an arcuatesupport portion and an arcuate liner portion configured to conform to aninner surface of the arcuate support portion. The first arcuate bearingsleeve assembly can be removably affixed to the first housing. The firstrotary actuator can also include a rotor assembly rotatably surroundingsaid first housing and defining a first central bore within an innerwall of the rotor assembly, and wherein the first arcuate bearing sleeveassembly is arranged radially between the first piston and the innerwall, and in contact with the radially outer side of the first pistonand the inner wall. The first arcuate bearing sleeve assembly can bearranged radially between the first piston and the inner wall, incontact with the radially outer side of the first piston and the innerwall. The rotary actuator can also include a fluid delivery shaft havingan elongated body, the fluid delivery shaft being disposed in a secondcentral bore defined by the first housing and in fluid communicationwith the first cavity. The rotor assembly can also include a rotaryoutput tube about the axis and a rotor arm in contact with a firstportion of the first piston, said rotor arm extending radially outwardto the rotary output tube and coupled to the rotary output tube. Therotary actuator can also include a second rotary actuator disposedwithin the first central bore. The second rotary actuator can include asecond housing defining a second arcuate chamber having a second cavityhaving a second open end, and an arcuate-shaped second piston disposedin said second housing for reciprocal movement in the second arcuatechamber through the second open end. The rotary actuator can alsoinclude a second arcuate bearing sleeve assembly, arranged radiallybetween the second piston and the inner wall, in contact with a radiallyouter side of the second piston and the inner wall. The first arcuatebearing sleeve can include a collection of bearings. The first arcuatebearing sleeve can include a friction-reducing coating.

An example method of rotary actuation includes providing a first rotaryactuator including a first housing defining first arcuate chamberincluding a first cavity having a first open end, and an arcuate-shapedfirst piston disposed in said first housing for reciprocal movement inthe first arcuate chamber through the first open end, wherein a firstseal, the first cavity, and the first piston define a first pressurechamber including part or all of the first arcuate chamber, and a firstarcuate bearing sleeve assembly having an inner surface configured to becontacted by a radially outer side of the first piston, urging the firstpiston partially rotationally outward from the first pressure chamber,and applying, by the first arcuate bearing sleeve portion, a firstradial force to the radially outer side of the piston.

Various implementations can include some, all, or none of the followingfeatures. The method can also include urging the first piston partiallyradially outward, contacting the first piston to the first arcuatebearing sleeve assembly with a second radial force, transmitting thesecond radial force to the first housing, and constraining, by firstarcuate bearing sleeve assembly, the second radial force. The method canalso include providing a second rotary actuator, wherein the rotorassembly rotatably surrounds the first rotary actuator and the secondrotary actuator. The method can also include redirecting the firstradial force through the first arcuate bearing sleeve assembly to arotor assembly rotatably surrounding said first housing and defining acentral bore within an inner wall of the rotor assembly, wherein thefirst arcuate bearing sleeve assembly is removably affixed to the firsthousing. The method can also include redirecting the first radial forcethrough the first arcuate bearing sleeve assembly to the first housing,wherein the first arcuate bearing sleeve assembly is removably affixedto the first housing. Applying, by the first arcuate bearing sleeveportion, a first radial force to the radially outer side of the pistoncan include applying the first radial force to a collection of bearingsin contact with the radially outer side of the piston. The first arcuatebearing sleeve portion can include a friction-reducing coating, andwherein applying, by the first arcuate bearing sleeve portion, a firstradial force to the radially outer side of the piston can also includeapplying the first radial force to the friction-reducing coating incontact with the radially outer side of the piston.

An example fluid actuator includes a housing defining a first chamberhaving a first cavity, a first fluid port in fluid communication withthe first cavity, and a first open end, a first piston assemblyincluding a tubular first piston defining a second chamber having asecond cavity, a second fluid port in fluid communication with thesecond cavity, and a second open end, disposed in said first housing forreciprocal movement in the first chamber through the first open end,wherein a first seal, the first cavity, and the first piston define afirst pressure chamber, and a second piston assembly including an secondpiston disposed in said first piston assembly for reciprocal movement inthe second chamber through the second open end, wherein a second seal,the second cavity, and the second piston define a second pressurechamber, and a first portion of the second piston contacts a first endeffector.

Various embodiments can include some, all, or none of the followingfeatures. The first chamber can be an arcuate first chamber includingthe first open end and a first enclosed end, the tubular first pistoncan be an arcuate-shaped tubular first piston, the second chamber can bean arcuate second chamber including the second open end and a secondenclosed end, the second piston can be an arcuate-shaped second piston,and the end effector can be a rotor arm. The housing can further definea third arcuate chamber having a third cavity, a third fluid port influid communication with the third cavity, and a third open end, thefirst piston assembly further includes an arcuate-shaped tubular thirdpiston defining a fourth arcuate chamber having a fourth cavity, afourth fluid port in fluid communication with the fourth cavity, and afourth open end, disposed in said first housing for reciprocal movementin the third arcuate chamber through the third open end, wherein a thirdseal, the third cavity, and the third piston define a third pressurechamber, and the second piston assembly further includes anarcuate-shaped fourth piston disposed in said first piston assembly forreciprocal movement in the fourth arcuate chamber through the fourthopen end, wherein a fourth seal, the fourth cavity, and the fourthpiston define a fourth pressure chamber, and a first portion of thefourth piston contacts a second end effector. The fluid actuator canalso include a rotor arm, wherein the first chamber can be an arcuatefirst chamber, the tubular first piston can be an arcuate-shaped tubularfirst piston, the second chamber can be an arcuate second chamber, thesecond piston can be an arcuate-shaped second piston, the third chambercan be an arcuate third chamber, the tubular third piston can be anarcuate-shaped tubular third piston, the fourth chamber can be anarcuate fourth chamber, the fourth piston can be an arcuate-shapedfourth piston, the first end effector can be the rotor arm, and thesecond end effector can be the rotor arm. The second piston can beoriented in the same rotational direction as the first piston. Thesecond piston can be oriented in the opposite rotational direction asthe first piston. Application of pressurized fluid to the third pressurechamber can urge the third piston partially outward from the thirdpressure chamber to urge rotation of the first piston assembly in afirst direction, application of pressurized fluid to the fourth pressurechamber can urge the fourth piston partially outward from the fourthpressure chamber to urge rotation of the second piston assembly in thefirst direction, rotation of the second piston assembly in a seconddirection opposite that of the first direction can urge the fourthpiston partially into the fourth pressure chamber to urge pressurizedfluid out the fourth fluid port, and rotation of the first pistonassembly in the second direction can urge the third piston partiallyinto the third pressure chamber to urge pressurized fluid out the thirdfluid port. The housing can further define an arcuate actuation spacedefining an actuation arc about the axis between the first open end anda terminal end, and the fluid actuator can also include a rotor assemblyincluding a rotary output tube rotatably surrounding said housing,wherein the rotor arm can extend radially outward to the rotary outputtube and the rotor arm is coupled to the rotary tube. The first seal canbe disposed about an interior surface of the first open end. The firstseal can be disposed about the periphery of the first piston and isconfigured to remain stationary relative to the first piston. The secondseal can be disposed about an interior surface of the second open end.The second seal can be disposed about the periphery of the second pistonand is configured to remain stationary relative to the second piston.The housing can be formed as a one-piece housing. The first piston canhave one of a square, rectangular, ovoid, elliptical, figure-eight, orcircular shape in cross-section. The first piston assembly can furtherdefine a fluid port fluidically connecting the first cavity and thesecond cavity. A first portion of the tubular first piston can contact asecond end effector.

An example method of fluid actuation includes providing a fluid actuatorincluding a housing defining a first chamber having a first cavity, afirst fluid port in fluid communication with the first cavity, and afirst open end, a first piston assembly including a tubular first pistondefining a second chamber having a second cavity, a second fluid port influid communication with the second cavity, and a second open end,disposed in said first housing for reciprocal movement in the firstchamber through the first open end, wherein a first seal, the firstcavity, and the first piston define a first pressure chamber, and asecond piston assembly includes an second piston disposed in said firstpiston assembly for reciprocal movement in the second chamber throughthe second open end, wherein a second seal, the second cavity, and thesecond piston define a second pressure chamber, and a first portion ofthe second piston contacts a first end effector, applying pressurizedfluid to the first pressure chamber, urging the first piston partiallyoutward from the first pressure chamber to urge the end effector in afirst direction, urging the end effector in a second direction oppositethat of the first direction, urging the first piston partially into thefirst pressure chamber to urge pressurized fluid out the first fluidport, applying pressurized fluid to the second pressure chamber, urgingthe second piston partially outward from the second pressure chamber tourge the first piston assembly in the first direction, urging the firstpiston assembly in the second direction, and urging the second pistonpartially into the second pressure chamber to urge pressurized fluid outthe second fluid port. The first chamber can be an arcuate first chamberhaving the first open end and a first enclosed end, the tubular firstpiston can be an arcuate-shaped tubular first piston, the second chambercan be an arcuate second chamber including the second open end and asecond enclosed end, the second piston can be an arcuate-shaped secondpiston, the end effector can be a rotor arm, urging the first pistonpartially outward from the first pressure chamber to urge the endeffector in a first direction can also include rotating the rotor arm inthe first direction with substantially constant torque over stroke, andurging the second piston partially outward from the second pressurechamber to urge the first piston assembly in the first direction canalso include rotating the first piston assembly in the first directionwith substantially constant torque over stroke.

An example arm of a machine apparatus includes a first arm portion, asecond arm portion, and a joint portion connecting the first arm portionto the second arm portion, the joint portion including a fluid actuatorhaving a housing defining a first chamber having a first cavity, a firstfluid port in fluid communication with the first cavity, and a firstopen end, a first piston assembly including a tubular first pistondefining a second chamber having a second cavity, a second fluid port influid communication with the second cavity, and a second open end,disposed in said first housing for reciprocal movement in the firstchamber through the first open end, wherein a first seal, the firstcavity, and the first piston define a first pressure chamber, and asecond piston assembly having an second piston disposed in said firstpiston assembly for reciprocal movement in the second chamber throughthe second open end, wherein a second seal, the second cavity, and thesecond piston define a second pressure chamber, and a first portion ofthe second piston contacts a first end effector.

Various embodiments can include some, all, or none of the followingfeatures. The end effector can be affixed to or can be integral to thefirst arm portion. The housing can be affixed to or can be integral tothe second arm portion.

An example multi-axis rotary actuator includes a first rotary pistonactuator configured to controllably actuate a first pivotal jointbetween a first linkage to a second linkage about a first axis, and asecond rotary piston actuator configured to controllably actuate asecond pivotal joint connecting the second linkage to a third linkageabout a second axis.

Various embodiments can include some, all, or none of the followingfeatures. The first axis can be parallel to the second axis. The firstaxis can be perpendicular to the second axis. The first axis canintersect the second axis. At least one of the first rotary pistonactuator and the second rotary piston actuator can include a housingdefining a first arcuate chamber having a first cavity defining a firstarc in a plane between a first open end and a first enclosed end andhaving a first fluid port in fluid communication with the first cavity,the first arc having a first radius in the plane, the first radiusdefining an axis perpendicular to the plane, and an arcuate actuationspace defining an actuation arc about the axis between the first openend and a terminal end, a rotor arm configured for rotary movementwithin the actuation space along a second arc, an arcuate-shaped firstpiston disposed in said housing for reciprocal movement in the firstarcuate chamber and in the plane through the first open end, wherein afirst seal, the first cavity, and the first piston define a firstpressure chamber including part or all of the first arcuate chamber, anda first portion of the first piston contacts the rotor arm, and a rotorassembly rotatably surrounding said housing and including a rotarycylinder about the axis, wherein the rotor arm extends radially outwardto the rotary cylinder and the rotor arm is coupled to the rotarycylinder, wherein the housing is coupled to a selected one of the firstlinkage, the second linkage, or the third linkage, and the rotorassembly is coupled to another one of the first linkage, the secondlinkage, or the third linkage. The multi-axis rotary actuator can alsoinclude a second arcuate chamber including a second cavity defining asecond arc about the axis between a second open end and a secondenclosed end and having a second fluid port in fluid communication withthe second cavity. The second arc can have a second radius from theaxis, different from the first radius. The second arc can be concentricwith the first arc about the axis in the plane. The second open end canbe at the terminal end, and the arcuate chamber can be orientedrotationally opposite to the first arcuate chamber about the axis. Thesecond arc is can be not in the plane and at least a portion of thesecond arcuate chamber can overlap axially with the first arcuatechamber in the plane. The multi-axis rotary actuator can also include anarcuate-shaped second piston disposed in said second housing forreciprocal movement in the second arcuate chamber through the secondopen end, wherein a second seal, the second cavity, and the secondpiston define a second pressure chamber including part or all of thesecond arcuate chamber, and a second portion of the second pistoncontacts the rotor arm. The rotor assembly can provide load bearingsupport for the housing. At least one of the first rotary pistonactuator and the second rotary piston actuator can include a housingdefining a first arcuate chamber housing defining a first arcuatechamber having a first cavity defining a first ring segment in a planebetween a first open end and a first enclosed end and having a firstfluid port in fluid communication with the first cavity, the ringsegment having a first outer radius in the plane, the first radiusdefining an axis perpendicular to the plane, a first inner radius in theplane, and a first central radius in the plane, a second arcuate chamberhaving an inner chamber wall defining a second cavity defining a secondring segment in the plane between a second open end and a secondenclosed end and having a second fluid port in fluid communication withthe second cavity, the second ring segment having a second outer radiusfrom the axis, larger than the first outer radius and concentric withthe first outer radius about the axis in the plane, a second innerradius smaller than the first inner radius in the plane, and a secondcentral radius substantially the same as the first central radius,wherein the second arcuate chamber is oriented rotationally opposite tothe first arcuate chamber about the axis and wherein at least a portionof the first arcuate chamber housing is enclosed within at least aportion of the second arcuate chamber in the plane and defining anarcuate tubular space between the first arcuate chamber housing and theinner chamber wall, and an arcuate actuation space defining a third arcin the plane about the axis between the first open end and the secondopen end, a rotor arm configured for rotary movement within theactuation space along the third arc, a rotor assembly coupled to therotor arm, an arcuate-shaped first piston disposed in said first housingfor reciprocal movement in the first arcuate chamber and in the planethrough the first open end, wherein a first seal, the first cavity, andthe first piston define a first pressure chamber, and a first portion ofthe first piston contacts a rotor arm, and a tubular, arcuate-shapedsecond piston disposed in said second housing for reciprocal movement inthe second arcuate chamber, in the arcuate tubular space and in theplane through the second open end, wherein a second seal, a third seal,the second cavity, and the second piston define a second pressurechamber, and a second portion of the second piston contacts the rotorarm, wherein the housing is coupled to a selected one of the firstlinkage, the second linkage, or the third linkage, and the rotorassembly is coupled to another one of the first linkage, the secondlinkage, or the third linkage.

An example method of multi-axis rotary actuation includes providing amulti-axis rotary actuator including a first rotary piston actuatorconfigured to controllably actuate a first pivotal joint between a firstlinkage to a second linkage about a first axis, and a second rotarypiston actuator configured to controllably actuate a second pivotaljoint connecting the second linkage to a third linkage about a secondaxis, applying pressurized fluid to the first rotary piston actuator,urging actuation of the first pivotal joint about the first axis in afirst direction, urging actuation of the first pivotal joint about thefirst axis in a second direction opposite that of the first direction,applying pressurized fluid to the second rotary piston actuator, urgingactuation of the second pivotal joint about the second axis in a thirddirection, and urging actuation of the second pivotal joint about thesecond axis in a fourth direction opposite that of the third direction.

Various implementations can include some, all, or none of the followingfeatures. Applying pressurized fluid to the first rotary piston actuatorcan also include applying pressurized fluid to a first pressure chamberof the first rotary piston actuator configured to urge actuation of thefirst pivotal joint in the first direction, and wherein applyingpressurized fluid to the second rotary piston actuator can also includeapplying pressurized fluid to a third pressure chamber of the secondrotary piston actuator configured to urge actuation of the secondpivotal joint in the third direction, and the method can also includeapplying pressurized fluid to a second pressure chamber of the firstrotary piston actuator configured to urge actuation of the first pivotaljoint in the second direction, urging actuation of the first pivotaljoint about the first axis in the second direction, applying pressurizedfluid to a fourth pressure chamber of the second rotary piston actuatorconfigured to urge actuation of the first pivotal joint in the seconddirection, and urging actuation of the second pivotal joint about thesecond axis in the fourth direction.

An example arm of a machine apparatus includes a first arm portion, asecond arm portion, and a joint portion pivotally connecting the firstarm portion to the second arm portion, the joint portion including amulti-axis rotary actuator including a first rotary piston actuatorconfigured to controllably actuate a first pivotal joint between a firstlinkage to a second linkage about a first axis, and a second rotarypiston actuator configured to controllably actuate a second pivotaljoint connecting the second linkage to a third linkage about a secondaxis.

Various embodiments can include some, all, or none of the followingfeatures. The first axis can be parallel to the second axis. The firstaxis can be perpendicular to the second axis. The first axis canintersect the second axis. At least one of the first rotary pistonactuator and the second rotary piston actuator can include a housingdefining a first arcuate chamber including a first cavity defining afirst arc in a plane between a first open end and a first enclosed endand having a first fluid port in fluid communication with the firstcavity, the first arc having a first radius in the plane, the firstradius defining an axis perpendicular to the plane, and an arcuateactuation space defining an actuation arc about the axis between thefirst open end and a terminal end, a rotor arm configured for rotarymovement within the actuation space along a second arc, anarcuate-shaped first piston disposed in said housing for reciprocalmovement in the first arcuate chamber and in the plane through the firstopen end, wherein a first seal, the first cavity, and the first pistondefine a first pressure chamber including part or all of the firstarcuate chamber, and a first portion of the first piston contacts therotor arm, and a rotor assembly rotatably surrounding said housing andincluding a rotary cylinder about the axis, wherein the rotor armextends radially outward to the rotary cylinder and the rotor arm iscoupled to the rotary cylinder, wherein the housing is coupled to aselected one of the first linkage, the second linkage, or the thirdlinkage, and the rotor assembly is coupled to another one of the firstlinkage, the second linkage, or the third linkage.

An example rotary piston actuator assembly includes a first rotaryactuator including a first housing defining a first central bore, and afirst arcuate chamber having a first cavity having a first actuatorfluid port in fluid communication with the first cavity and the firstcentral bore, a rotor arm, an arcuate-shaped first piston disposed insaid first housing for reciprocal movement in the first housing, whereina first seal, the first cavity, and the first piston define a firstpressure chamber having part or all of the first arcuate chamber, and afirst portion of the first piston contacts the rotor arm, a rotorassembly rotatably surrounding said first housing and including a rotaryoutput tube, wherein the rotor arm extends radially outward to therotary output tube and the rotor arm is coupled to the rotary tube, anda fluid delivery shaft having an elongated body disposed in said firstcentral bore and defining a first shaft fluid delivery path.

Various embodiments can include some, all, or none of the followingfeatures. The rotary piston actuator assembly can also include a secondrotary actuator including a second housing defining a second centralbore, a second arcuate chamber having a second cavity having a secondactuator fluid port in fluid communication with the second cavity andthe second central bore, and an arcuate-shaped second piston disposed insaid second housing for reciprocal movement in the second housing,wherein a second seal, the second cavity, and the second piston define asecond pressure chamber having part or all of the second arcuatechamber, and a first portion of the second piston contacts the rotorarm, wherein the rotor assembly rotatably surrounds said second housing,and the fluid delivery shaft is disposed in said second central bore.The fluid delivery shaft can define an axis and can include a firstshaft fluid port along the body, a second shaft fluid port near aterminal end of the body, and the first shaft fluid delivery pathdefined by the fluid delivery shaft and fluidly connecting the firstshaft fluid port to the second shaft fluid port, a first shaft sealdisposed about the fluid delivery shaft on a first axial side of thefirst shaft fluid port along the axis, a second shaft seal disposedabout the fluid delivery shaft on a second axial side of the first shaftfluid port along the axis and opposite the first shaft seal, wherein thefirst central bore, the body, the first shaft fluid seal, and the secondshaft fluid seal define a first fluid transmission chamber, and thefirst actuator fluid port is in fluidic communication with the firstfluid transmission chamber. The first central bore can also define afirst bore portion and a second bore portion, wherein the first boreportion extends along substantially a first half of the axial length ofthe first central bore, and the second bore portion extends alongsubstantially the second half of the axial length of the first centralbore, and the first actuator fluid port is defined within the first boreportion, wherein the first fluid transmission chamber can extend alongsubstantially one half of the axial length of the first central boresuch that the first fluid transmission chamber extends along the firstbore portion in a first assemblage of the first rotary actuator and thefluid delivery shaft, and the first fluid transmission chamber canextend along the second bore portion in a second assemblage of the firstrotary actuator and the fluid delivery shaft. The first arcuate chambercan also define a first open end, and the first piston can also includea first piston assembly having a tubular first piston defining a secondchamber having a second cavity, a second fluid port in fluidcommunication with the second cavity, and a second open end, disposed insaid first housing for reciprocal movement in the first chamber throughthe first open end, wherein a first seal, the first cavity, and thefirst piston define a first pressure chamber, and the rotary pistonactuator can also include a second piston assembly including an secondpiston disposed in said first piston assembly for reciprocal movement inthe second chamber through the second open end, wherein a second seal,the second cavity, and the second piston define a second pressurechamber, and a first portion of the second piston contacts a first endeffector. The first cavity can define a first arc in a plane between afirst open end and a first enclosed end and having a first fluid port influid communication with the first cavity, the first arc having a firstradius in the plane, the first radius defining an axis perpendicular tothe plane, and the first housing further defines an arcuate actuationspace defining an actuation arc about the axis between the first openend and a terminal end, wherein the rotor arm is configured for rotarymovement within the actuation space along a second arc, and the firstpiston is disposed in said first housing for reciprocal movement in thefirst arcuate chamber and in the plane through the first open end,wherein the first seal, the first cavity, and the first piston definethe first pressure chamber including part or all of the first arcuatechamber. The first housing can include a first arcuate chamber housingdefining the first arcuate chamber, wherein the first cavity defines afirst ring segment in a plane between a first open end and a firstenclosed end, the ring segment having a first outer radius in the planeand defining an axis perpendicular to the plane, a first inner radius inthe plane about the axis, and a first central radius in the plane,wherein the first housing further defines a second arcuate chamberhaving an inner chamber wall defining a second cavity defining a secondring segment in the plane between a second open end and a secondenclosed end and having a second fluid port in fluid communication withthe second cavity, the second ring segment having a second outer radiusfrom the axis, larger than the first outer radius and concentric withthe first outer radius about the axis in the plane, a second innerradius smaller than the first inner radius in the plane, and a secondcentral radius substantially the same as the first central radius,wherein the second arcuate chamber is oriented rotationally opposite tothe first arcuate chamber about the axis and wherein at least a portionof the first arcuate chamber housing is enclosed within at least aportion of the second arcuate chamber in the plane and defining anarcuate tubular space between the first arcuate chamber housing and theinner chamber wall, and an arcuate actuation space defining a third arcin the plane about the axis between the first open end and the secondopen end, and the rotor arm is configured for rotary movement within theactuation space along the third arc, wherein the arcuate-shaped firstpiston disposed in said first housing for reciprocal movement in thefirst arcuate chamber and in the plane through the first open end,wherein the first seal, the first cavity, and the first piston definethe first pressure chamber, and wherein the rotary piston actuatorassembly also includes a tubular, arcuate-shaped second piston disposedin said second housing for reciprocal movement in the second arcuatechamber, in the arcuate tubular space and in the plane through thesecond open end, wherein a second seal, a third seal, the second cavity,and the second piston define a second pressure chamber, and a secondportion of the second piston contacts the rotor arm.

An example method of rotary actuation includes providing a first rotaryactuator including a first housing defining a first central bore, and afirst arcuate chamber including a first cavity having a first actuatorfluid port in fluid communication with the first cavity and the firstcentral bore, a rotor arm, an arcuate-shaped first piston disposed insaid first housing for reciprocal movement in the first housing, whereina first seal, the first cavity, and the first piston define a firstpressure chamber including part or all of the first arcuate chamber, anda first portion of the first piston contacts the rotor arm, a rotorassembly rotatably surrounding said first housing and including a rotaryoutput tube, wherein the rotor arm extends radially outward to therotary output tube and the rotor arm is coupled to the rotary tube, anda fluid delivery shaft having an elongated body disposed in said firstcentral bore and defining a first shaft fluid delivery path, providingpressurized fluid to the second shaft fluid port, urging pressurizedfluid to the first pressure chamber through the first shaft fluiddelivery path, the first shaft fluid port, the first fluid transmissionchamber, and the first fluid port, urging the first piston partiallyoutward from the first pressure chamber to urge rotation of the rotorassembly in a first direction, rotating the rotor assembly in a seconddirection opposite that of the first direction, and urging the firstpiston partially into the first pressure chamber to urge pressurizedfluid out the second shaft fluid port through the first fluid port, thefirst fluid transmission chamber, the first shaft fluid port, and thefirst shaft fluid delivery path.

Various implementations can include some, all, or none of the followingfeatures. The method can also include disassembling the first rotaryactuator from a first assembly configuration with the fluid deliveryshaft, reassembling the first rotary actuator to the fluid deliveryshaft in a second configuration, providing pressurized fluid to thesecond shaft fluid port, urging pressurized fluid to the first pressurechamber through the first shaft fluid delivery path, the first shaftfluid port, the first fluid transmission chamber, and the first fluidport, urging the first piston partially outward from the first pressurechamber to urge rotation of the rotor assembly in the second direction,rotating the rotor assembly in the direction opposite that of the seconddirection, and urging the first piston partially into the first pressurechamber to urge pressurized fluid out the second shaft fluid portthrough the first fluid port, the first fluid transmission chamber, thefirst shaft fluid port, and the first shaft fluid delivery path. Thefirst central bore can define a first bore portion and a second boreportion, wherein the first bore portion extends along substantially afirst half of the axial length of the first central bore, and the secondbore portion extends along substantially the second half of the axiallength of the first central bore, and the first actuator fluid port isdefined within the first bore portion; and wherein the first fluidtransmission chamber extends along substantially one half of the axiallength of the first central bore such that the first fluid transmissionchamber extends along the first bore portion in a first assemblage ofthe first rotary actuator and the fluid delivery shaft, and the firstfluid transmission chamber extends along the second bore portion in asecond assemblage of the first rotary actuator and the fluid deliveryshaft. The method can also include disassembling the first rotaryactuator from a first assembly configuration with the fluid deliveryshaft, wherein the first central bore portion, the body, the first shaftfluid seal, and the second shaft fluid seal define the first fluidtransmission chamber in the first configuration, reassembling the firstrotary actuator to the fluid delivery shaft in a second configuration,wherein the second central bore portion, the body, the first shaft fluidseal, and the second shaft fluid seal define the first fluidtransmission chamber in the second configuration, providing pressurizedfluid to the second shaft fluid port, and blocking flow of pressurizedfluid by the first pressure chamber.

Another example arm of a machine apparatus includes a first arm portion,a second arm portion, and a joint portion pivotally connecting the firstarm portion to the second arm portion, the joint portion having a firstrotary actuator including a first housing defining a first central bore,and a first arcuate chamber having a first cavity having a firstactuator fluid port in fluid communication with the first cavity and thefirst central bore, and a rotor arm, an arcuate-shaped first pistondisposed in said first housing for reciprocal movement in the firsthousing, wherein a first seal, the first cavity, and the first pistondefine a first pressure chamber including part or all of the firstarcuate chamber, and a first portion of the first piston contacts therotor arm, a rotor assembly rotatably surrounding said first housing andincluding a rotary output tube, wherein the rotor arm extends radiallyoutward to the rotary output tube and the rotor arm is coupled to therotary tube, and a fluid delivery shaft having an elongated bodydisposed in said first central bore and defining a first shaft fluiddelivery path.

Various embodiments can include some, all, or none of the followingfeatures. The rotor assembly can be affixed to or can be integral to thefirst arm portion. The housing can be affixed to or can be integral tothe second arm portion. The arm can also include a second rotaryactuator including a second housing defining a second central bore, asecond arcuate chamber having a second cavity having a second actuatorfluid port in fluid communication with the second cavity and the secondcentral bore, and an arcuate-shaped second piston disposed in saidsecond housing for reciprocal movement in the second housing, wherein asecond seal, the second cavity, and the second piston define a secondpressure chamber including part or all of the second arcuate chamber,and a first portion of the second piston contacts the rotor arm, whereinthe rotor assembly rotatably surrounds said second housing, and thefluid delivery shaft is disposed in said second central bore. The fluiddelivery shaft can define an axis and can include a first shaft fluidport along the body, a second shaft fluid port near a terminal end ofthe body, and the first shaft fluid delivery path defined by the fluiddelivery shaft and fluidly connecting the first shaft fluid port to thesecond shaft fluid port, a first shaft seal disposed about the fluiddelivery shaft on a first axial side of the first shaft fluid port alongthe axis, a second shaft seal disposed about the fluid delivery shaft ona second axial side of the first shaft fluid port along the axis andopposite the first shaft seal, wherein the first central bore, the body,the first shaft fluid seal, and the second shaft fluid seal define afirst fluid transmission chamber, and the first actuator fluid port isin fluidic communication with the first fluid transmission chamber. Thefirst central bore can further define a first bore portion and a secondbore portion, wherein the first bore portion extends along substantiallya first half of the axial length of the first central bore, and thesecond bore portion extends along substantially the second half of theaxial length of the first central bore, and the first actuator fluidport is defined within the first bore portion, wherein the first fluidtransmission chamber extends along substantially one half of the axiallength of the first central bore such that the first fluid transmissionchamber extends along the first bore portion in a first assemblage ofthe first rotary actuator and the fluid delivery shaft, and the firstfluid transmission chamber extends along the second bore portion in asecond assemblage of the first rotary actuator and the fluid deliveryshaft.

Another example rotary actuator includes a housing defining a firstarcuate chamber housing defining a first arcuate chamber including afirst cavity defining a first ring segment in a plane between a firstopen end and a first enclosed end and having a first fluid port in fluidcommunication with the first cavity, the ring segment having a firstouter radius in the plane and defining an axis perpendicular to theplane, a first inner radius in the plane about the axis, and a firstcentral radius in the plane, a second arcuate chamber including an innerchamber wall defining a second cavity defining a second ring segment inthe plane between a second open end and a second enclosed end and havinga second fluid port in fluid communication with the second cavity, thesecond ring segment having a second outer radius from the axis, largerthan the first outer radius and concentric with the first outer radiusabout the axis in the plane, a second inner radius smaller than thefirst inner radius in the plane, and a second central radiussubstantially the same as the first central radius, wherein the secondarcuate chamber is oriented rotationally opposite to the first arcuatechamber about the axis and wherein at least a portion of the firstarcuate chamber housing is enclosed within at least a portion of thesecond arcuate chamber in the plane and defining an arcuate tubularspace between the first arcuate chamber housing and the inner chamberwall, and an arcuate actuation space defining a third arc in the planeabout the axis between the first open end and the second open end, arotor arm configured for rotary movement within the actuation spacealong the third arc, a rotor assembly coupled to the rotor arm, anarcuate-shaped first piston disposed in said first housing forreciprocal movement in the first arcuate chamber and in the planethrough the first open end, wherein a first seal, the first cavity, andthe first piston define a first pressure chamber, and a first portion ofthe first piston contacts a rotor arm, and a tubular, arcuate-shapedsecond piston disposed in said second housing for reciprocal movement inthe second arcuate chamber, in the arcuate tubular space and in theplane through the second open end, wherein a second seal, a third seal,the second cavity, and the second piston define a second pressurechamber, and a second portion of the second piston contacts the rotorarm.

Various embodiments can include some, all, or none of the followingfeatures. At least a portion of the second arcuate chamber can overlapaxially with the first arcuate chamber in the plane. The rotor assemblycan be rotatably journaled in said housing and can include a rotaryoutput shaft along the axis, wherein the rotor arm extends radiallyinward to the rotary output shaft and the rotor arm is coupled to therotary output shaft. The rotor assembly can rotatably surround saidhousing and can include a rotary output cylinder about the axis, whereinthe rotor arm extends radially outward to the rotary output cylinder andthe rotor arm is coupled to the rotary output cylinder. The first sealcan be disposed about an interior surface of the open end and can beconfigured to remain stationary relative to the open end. The first sealcan be disposed about the periphery of the first piston and can beconfigured to remain stationary relative to the first portion. The firstseal can provide load bearing support for the first piston. The rotorassembly can provide load bearing support for the housing. The housingcan be formed as a one-piece housing. The first seal can be a one-pieceseal. The first piston can be solid in cross-section. At least one ofthe first piston and the second piston can be at least partly hollow incross-section. The first piston can have one of a square, rectangular,ovoid, elliptical, figure-eight, or circular shape in cross-section.

Another example method of rotary actuation includes providing a rotaryactuator including a housing defining a first arcuate chamber housingdefining a first arcuate chamber including a first cavity defining afirst ring segment in a plane between a first open end and a firstenclosed end and having a first fluid port in fluid communication withthe first cavity, the ring segment having a first outer radius in theplane and defining an axis perpendicular to the plane, a first innerradius in the plane about the axis, and a first central radius in theplane, a second arcuate chamber having an inner chamber wall defining asecond cavity defining a second ring segment in the plane between asecond open end and a second enclosed end and having a second fluid portin fluid communication with the second cavity, the second ring segmenthaving a second outer radius from the axis, larger than the first outerradius and concentric with the first outer radius about the axis in theplane, a second inner radius smaller than the first inner radius in theplane, and a second central radius substantially the same as the firstcentral radius, wherein the second arcuate chamber is orientedrotationally opposite to the first arcuate chamber about the axis andwherein at least a portion of the first arcuate chamber housing isenclosed within at least a portion of the second arcuate chamber in theplane and defining an arcuate tubular space between the first arcuatechamber housing and the inner chamber wall, and an arcuate actuationspace defining a third arc in the plane about the axis between the firstopen end and the second open end, a rotor arm configured for rotarymovement within the actuation space along the third arc, a rotorassembly coupled to the rotor arm, an arcuate-shaped first pistondisposed in said first housing for reciprocal movement in the firstarcuate chamber and in the plane through the first open end, wherein afirst seal, the first cavity, and the first piston define a firstpressure chamber, and a first portion of the first piston contacts arotor arm, and a tubular, arcuate-shaped second piston disposed in saidsecond housing for reciprocal movement in the second arcuate chamber, inthe arcuate tubular space and in the plane through the second open end,wherein a second seal, a third seal, the second cavity, and the secondpiston define a second pressure chamber, and a second portion of thesecond piston contacts the rotor arm, applying pressurized fluid to thefirst pressure chamber, urging the first piston partially outward fromthe first pressure chamber to urge movement of the rotor arm in a firstdirection, rotating the rotor arm in a second direction opposite that ofthe first direction, and urging the first piston partially into thefirst pressure chamber to urge pressurized fluid out the first fluidport.

Various implementations can include some, all, or none of the followingfeatures. Rotating the rotor arm in a second direction opposite that ofthe first direction can include applying pressurized fluid to the secondpressure chamber, and urging the second piston partially outward fromthe second pressure chamber to urge movement of the rotor arm in asecond direction opposite from the first direction. Urging the firstpiston partially outward from the first pressure chamber to urgemovement of the rotor arm in a first direction can also include movingthe rotor arm in the first direction with substantially constant torqueover stroke.

Another example arm of a machine apparatus includes a first arm portion,a second arm portion, and a joint portion pivotally connecting the firstarm portion to the second arm portion, the joint portion including arotary actuator including a housing defining a first arcuate chamberhousing defining a first arcuate chamber having a first cavity defininga first ring segment in a plane between a first open end and a firstenclosed end and having a first fluid port in fluid communication withthe first cavity, the ring segment having a first outer radius in theplane and defining an axis perpendicular to the plane, a first innerradius in the plane about the axis, and a first central radius in theplane, a second arcuate chamber having an inner chamber wall defining asecond cavity defining a second ring segment in the plane between asecond open end and a second enclosed end and having a second fluid portin fluid communication with the second cavity, the second ring segmenthaving a second outer radius from the axis, larger than the first outerradius and concentric with the first outer radius about the axis in theplane, a second inner radius smaller than the first inner radius in theplane, and a second central radius substantially the same as the firstcentral radius, wherein the second arcuate chamber is orientedrotationally opposite to the first arcuate chamber about the axis andwherein at least a portion of the first arcuate chamber housing isenclosed within at least a portion of the second arcuate chamber in theplane and defining an arcuate tubular space between the first arcuatechamber housing and the inner chamber wall, and an arcuate actuationspace defining a third arc in the plane about the axis between the firstopen end and the second open end, a rotor arm configured for rotarymovement within the actuation space along the third arc, a rotorassembly coupled to the rotor arm, an arcuate-shaped first pistondisposed in said first housing for reciprocal movement in the firstarcuate chamber and in the plane through the first open end, wherein afirst seal, the first cavity, and the first piston define a firstpressure chamber, and a first portion of the first piston contacts arotor arm, and a tubular, arcuate-shaped second piston disposed in saidsecond housing for reciprocal movement in the second arcuate chamber, inthe arcuate tubular space and in the plane through the second open end,wherein a second seal, a third seal, the second cavity, and the secondpiston define a second pressure chamber, and a second portion of thesecond piston contacts the rotor arm.

Various embodiments can include some, all, or none of the followingfeatures. The rotor assembly can be affixed to or can be integral to thefirst arm portion. The housing can be affixed to or can be integral tothe second arm portion.

Another example rotary actuator includes a housing defining a firstarcuate chamber including a first cavity defining a first arc in a planebetween a first open end and a first enclosed end and having a firstfluid port in fluid communication with the first cavity, the first archaving a first radius in the plane, the first radius defining an axisperpendicular to the plane, and an arcuate actuation space defining anactuation arc about the axis between the first open end and a terminalend, a rotor arm configured for rotary movement within the actuationspace along a second arc, an arcuate-shaped first piston disposed insaid housing for reciprocal movement in the first arcuate chamber and inthe plane through the first open end, wherein a first seal, the firstcavity, and the first piston define a first pressure chamber includingpart or all of the first arcuate chamber, and a first portion of thefirst piston contacts the rotor arm, and a rotor assembly rotatablysurrounding said housing and having a rotary output tube about the axis,wherein the rotor arm extends radially outward to the rotary output tubeand the rotor arm is coupled to the rotary tube.

Various embodiments can include some, all, or none of the followingfeatures. The rotary actuator can also include a second arcuate chamberhaving a second cavity defining a second arc about the axis between asecond open end and a second enclosed end and having a second fluid portin fluid communication with the second cavity. The second arc can have asecond radius from the axis, different than the first radius. The secondarc can be concentric with the first arc about the axis in the plane.The second open end can be at the terminal end, and the arcuate chambercan be oriented rotationally opposite to the first arcuate chamber aboutthe axis. The second arc is can be not in the plane and at least aportion of the second arcuate chamber can overlap axially with the firstarcuate chamber in the plane. The rotary actuator can also include anarcuate-shaped second piston disposed in said second housing andconfigured for reciprocal movement in the second arcuate chamber throughthe second open end, wherein a second seal, the second cavity, and thesecond piston define a second pressure chamber including part or all ofthe second arcuate chamber, and a second portion of the second pistoncontacts the rotor arm. Application of pressurized fluid to the firstpressure chamber can urge the first piston partially outward from thefirst pressure chamber to urge rotation of the rotor arm in a firstdirection, and application of pressurized fluid to the second pressurechamber can urge the second piston partially outward from the secondpressure chamber to urge rotation of the rotor arm in a seconddirection. At least one of the first piston and the second piston caninclude the rotor arm. Rotation of the rotor assembly can urge the firstpiston partially into the first pressure chamber to pressurize a fluidand urge the fluid out of the first fluid port. The rotary tube caninclude the rotor arm. The rotary actuator can also include a firsthousing seal ring groove defined in the rotor assembly about the axis, asecond housing seal ring groove defined in the housing about the axisand complimentary to the first housing seal ring groove, and aring-shaped seal between the rotor assembly and the housing within thefirst housing seal ring groove and the second housing seal ring groove.

Another example method of rotary actuation can include providing arotary actuator including a housing defining a first arcuate chamberhaving a first cavity defining a first arc in a plane between a firstopen end and a first enclosed end and having a first fluid port in fluidcommunication with the first cavity, the first arc having a first radiusin the plane, the first radius defining an axis perpendicular to theplane, and an arcuate actuation space defining an actuation arc aboutthe axis between the first open end and a terminal end, a rotor armconfigured for rotary movement within the actuation space along a secondarc, an arcuate-shaped first piston disposed in said housing forreciprocal movement in the first arcuate chamber and in the planethrough the first open end, wherein a first seal, the first cavity, andthe first piston define a first pressure chamber including part or allof the first arcuate chamber, and a first portion of the first pistoncontacts the rotor arm, and a rotor assembly rotatably surrounding saidhousing and having a rotary output tube about the axis, wherein therotor arm extends radially outward to the rotary output tube and therotor arm is coupled to the rotary tube, applying pressurized fluid tothe first pressure chamber, urging the first piston partially outwardfrom the first pressure chamber to urge rotation of the rotor assemblyin a first direction, rotating the rotor assembly in a second directionopposite that of the first direction, and urging the first pistonpartially into the first pressure chamber to urge pressurized fluid outthe first fluid port.

Various implementations can include some, all, or none of the followingfeatures. The housing can further define a second arcuate chamber havinga second cavity defining a second arc about the axis between a secondopen end and a second enclosed end and having a second fluid port influid communication with the second cavity, the rotary actuator canfurther include an arcuate-shaped second piston disposed in said firsthousing for reciprocal movement in the second arcuate chamber, wherein asecond seal, the second cavity, and the second piston define a secondpressure chamber, and a first portion of the second piston contacts thesecond rotor arm. The second piston can be oriented in the samerotational direction as the first piston. The second piston can beoriented in the opposite rotational direction as the first piston.Rotating the rotor assembly in a second direction opposite that of thefirst direction can include applying pressurized fluid to the secondpressure chamber, and urging the second piston partially outward fromthe second pressure chamber to urge rotation of the rotor assembly in asecond direction opposite from the first direction. Rotating the rotorassembly in a second direction opposite that of the first direction caninclude applying pressurized fluid to the second pressure chamber, andurging the first piston partially into the first pressure chamber tourge rotation of the rotor assembly in a second direction opposite fromthe first direction. Urging the first piston partially outward from thefirst pressure chamber to urge rotation of the rotor assembly in a firstdirection can also include rotating the rotor assembly in the firstdirection with substantially constant torque over stroke.

Another example arm of a machine apparatus includes a first arm portion,a second arm portion, and a joint portion pivotally connecting the firstarm portion to the second arm portion, the joint portion including arotary actuator including a housing defining a first arcuate chamberhaving a first cavity defining a first arc in a plane between a firstopen end and a first enclosed end and having a first fluid port in fluidcommunication with the first cavity, the first arc having a first radiusin the plane, the first radius defining an axis perpendicular to theplane, and an arcuate actuation space defining an actuation arc aboutthe axis between the first open end and a terminal end, a rotor armconfigured for rotary movement within the actuation space along a secondarc, an arcuate-shaped first piston disposed in said housing forreciprocal movement in the first arcuate chamber and in the planethrough the first open end, wherein a first seal, the first cavity, andthe first piston define a first pressure chamber including part or allof the first arcuate chamber, and a first portion of the first pistoncontacts the rotor arm, and a rotor assembly rotatably surrounding saidhousing and including a rotary output tube about the axis, wherein therotor arm extends radially outward to the rotary output tube and therotor arm is coupled to the rotary tube.

Various embodiments can include some, all, or none of the followingfeatures. The rotor assembly can be affixed to or can be integral to thefirst arm portion. The housing can be affixed to or can be integral tothe second arm portion.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features andadvantages will be apparent from the description and drawings, and fromthe claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of an example excavator having linear fluidactuators.

FIG. 2 is a diagram that shows an example of an articulated boom havingrotary piston actuators.

FIG. 3 is a partial cutaway view of an example rotary piston actuatorjoint portion.

FIG. 4 is a partial cutaway view of another example rotary pistonactuator joint portion.

FIG. 5 is an exploded view of an example rotary piston actuator jointportion.

FIGS. 6A and 6B are sectional end and perspective views of an examplerotary piston actuator with concentric pistons.

FIGS. 7A and 7B are sectional end and perspective views of an examplerotary piston actuator with spatially co-located pistons.

FIGS. 8A and 8B are sectional end and perspective views of an examplerotary piston actuator with multi-chamber pistons.

FIG. 9 is an exploded view of an example rotary piston actuator jointportion having modular rotary piston actuators.

FIG. 10 is a sectional view of an example fluid delivery shaft.

FIG. 11 is a sectional view of another example fluid delivery shaft.

FIG. 12 is a flow diagram of an example process for performing rotaryactuation.

FIG. 13 is a perspective view of an example rotary piston actuator jointportion having arcuate bearing sleeve assemblies.

FIG. 14 is an exploded view of an example arcuate bearing sleeveassembly for rotary piston actuators.

FIGS. 15A and 15B are a sectional side view and exploded view,respectively, of another example rotary piston actuator having anarcuate bearing sleeve assembly.

FIG. 16 is a sectional side view of another example arcuate bearingsleeve assembly.

FIG. 17 is a sectional side view of another example arcuate bearingsleeve assembly.

FIG. 18 is a flow diagram of an example process for performing rotaryactuation of an example rotary piston actuator joint portion havingarcuate bearing sleeve assemblies.

DETAILED DESCRIPTION

This document describes devices for producing rotary motion. Inparticular, this document describes devices that can convert fluiddisplacement into rotary motion through the use of components morecommonly used for producing linear motion, e.g., hydraulic or pneumaticlinear cylinders. Vane-type rotary actuators are relatively compactdevices used to convert fluid motion into rotary motion.

FIG. 1 is a diagram of an example prior art excavator 100. The excavator100 includes a “house” or “cab” 110 that rides on a tracked, wheeled,other generally otherwise mobile undercarriage 120. An articulated boom130, which includes an arm portion 132 and an arm portion 134, extendsfrom the house 110. The arm portion 132 and the arm portion 134 arepivotably connected at a joint 135. The arm portion 134 and a bucket 140are pivotably connected at a joint 142. A linear piston 150 and a linearpiston 160 provide power to actuate the arm portion 134 and the bucket140, e.g., to manipulate the bucket 140 for digging, shoveling, lifting,or other such operations.

Linear pistons use relatively mature sealing technology that exhibitswell-understood dynamic operation and leakage characteristics. Linearpistons, however, require additional mechanical components in order toadapt their linear motions to rotary motions. In the illustratedexample, the linear piston 150 is connected at one end to the armportion 132 and at the other end to a lever arm 136 that extends beyondthe joint 135. A linear piston 160 is connected at one end to the armportion 134 and at the other end to a lever arm assembly 162 thatextends beyond the joint 142. By extending and retracting the linearactuator 150, the lever arm 138 is actuated and a moment is createdabout the joint 136 to convert the linear motion of the linear actuator150 to rotary motion of the arm portion 134 relative to the arm portion132. A linear actuator 160 is arranged in a similar linear-to-rotaryconfiguration to pivotably actuate the bucket 140 relative to the armportion 134.

Such linear-to-rotary mechanisms are generally larger and heavier thanrotary actuators that are capable of providing similar rotationalactions, e.g., occupying a larger work envelope. In general, rotarypiston assemblies use curved pressure chambers and curved pistons tocontrollably push and pull the rotor arms of a rotor assembly about anaxis. Prior rotary piston assemblies, however, are generally larger andheavier than linear-to-rotary mechanisms that are capable of providingsimilar torque and load handling capacities. The rotary pistonassemblies described herein can provide the positional holding andpower/torque characteristics generally associated with linearpiston-type fluid actuators, to rotary applications, and can do so usingrelatively more compact and lightweight envelopes.

Linear-to-rotary mechanisms such as those used in the excavator 100 canalso expose many of their components to contamination. For example, thelinear pistons 150 and 160 can expose polished or otherwise sensitivesurfaces to dirt, dust, and other such contaminants typicallyencountered at construction sites. In another example, the linearpistons 150 and 160 may be exposed to liquid contaminants such as rainor mud (e.g., the linear piston 160 may be partly submerged during adigging operation). In yet another example, sensitive portions of thelinear pistons 150 and 160 can be exposed to physical damage, e.g., acollision with a solid object. Solid contaminants and physicalcollisions can harm polished surfaces and seals, leading to leaks andreductions in hydraulic performance. Fluid contaminants can invadehydraulic systems and harm hydraulic pumps, hoses, and seals. In someexamples, the various moving parts of the joints 135 and 142, the leverarm 136, and the lever arm assembly 162 may also present multiple pointsfor such contamination and damage.

In some embodiments, the rotary piston assemblies described herein canprovide relatively greater resistance to contamination, and/orrelatively easier maintenance than linear-to-rotary assemblies havingsimilar positional holding and power/torque characteristics.

Furthermore, linear-to-rotary mechanisms such as those used in theexcavator 100 can have relatively limited ranges of motion and canexhibit torque and/or motion characteristics that vary across the rangeof motion. For example, the range of motion between the arm portion 132and the arm portion 134 can be mechanically limited at one extreme(e.g., approximately the position shown in FIG. 1) by the linear piston150 contacting the arm portion 132 as the linear piston 150 extends. Therange can be limited at the other extreme, for example, by the lever arm136 contacting the arm portion 132 or by the arm portion 136 becomingsubstantially aligned between the linear piston 150 and the joint 135 asthe linear piston 150 retracts.

In some embodiments, the rotary piston assemblies described herein canprovide relatively greater ranges of motion, greater angular velocity,and/or more constant angular velocity across their ranges of motion thanlinear-to-rotary assemblies used for similar applications.

As the linear piston 150 extends and retracts at a constant rate, theangular velocity of the arm portion 134 and the torque developed aboutthe joint 135 will vary. For example, for a constant rate of linearactuation the arm portion 134 can have the greatest angular velocity andtorque when the lever arm 136 is at approximately a right angle to thelinear piston 150, with the speed and torque being lowest at the extremeranges of motion where the angles between the lever arm 136 and thelinear piston are the smallest. Prior excavators such as the excavator100 required operators to overcome this variability manually or byimplementing complex fluid control systems to operate the linear pistonsin a non-linear manner that provided a more constant motion. Some priorexcavators such as the excavator 100 implement oversized linear pistonsin order to compensate for the loss of torque inherent in manylinear-to-rotary configurations, but such oversizing often comes withadditional weight and cost.

In some embodiments, the rotary piston assemblies described herein canprovide relatively greater ranges of motion and/or relatively morelinear torque across angles of actuation than linear-to-rotaryassemblies used in similar applications.

FIG. 2 is a diagram that shows an example of an articulated boom 200(e.g., and excavator boom) having rotary piston actuators. In someimplementations, the articulated boom 200 can be used on an excavator.For the purposes of the descriptions here, the term “excavator” caninclude diggers, trenchers, backhoes, drilling rigs, cranes, bulldozers,robotic actuators or any other appropriate form of constructionequipment having rotary or pivotably articulated joints.

The articulated boom 200, includes an arm portion 210 and bucket 220. Insome embodiments, the arm portion 210 can be connected at an end 212 toanother arm portion or to a house or cab of an excavator. In someimplementations, the bucket 220 may be replaced by another type of endeffector, such as a bulldozer blade, a pulley (e.g., a crane), a drill,a trencher, a claw, a gripper, a fork, or any other appropriate form ofend effector that can be used with heavy equipment.

The arm portion 210 and the bucket are connected by a multi-axis fluidactuator. The multi-axis fluid actuator is configured to manipulate thebucket 220 for digging, shoveling, lifting, or other such operations.The multi-axis fluid actuator includes a joint 240 and a joint 250. Thejoint 240 includes a rotary piston actuator that pivotably connects ajoint arm 260 to a joint arm 262 about a first axis. The joint 240 andthe rotary piston actuator will be described in more detail in thedescription of FIG. 3. The joint 250 includes another rotary pistonactuator that pivotably connects the joint arm 262 to a joint arm 264about a second axis. The joint 250 and the rotary piston actuator willbe described in more detail in the description of FIGS. 4 and 5. Themulti-axis fluid actuator is removably connected (e.g., bolted, pinned)to the arm portion 210 by the joint arm 260, and is removably connectedto the bucket 220 by the joint arm 264. The joint 240 and the joint 250are configured to provide two axes of motion between the bucket 220 andthe arm portion 210.

FIG. 3 is a partial cutaway view of the example joint 240 of FIG. 2. Thejoint 240 includes a rotary piston actuator 300. In general, rotarypiston actuators use curved pressure chambers and curved pistons tocontrollably push and pull the rotor arms of a rotor assembly about anaxis. In use, certain embodiments of the rotary piston actuatorsdescribed herein can provide the positional holding characteristicsgenerally associated with linear piston-type fluid actuators, to rotaryapplications, and can do so using the relatively more compact andlightweight envelopes generally associated with rotary vane actuators.

The actuator 300 includes a rotary piston assembly 310 and a pressurechamber assembly 320. The actuator 300 includes a first actuationsection 360 and a second actuation section 370. In the example ofactuator 300, the first actuation section 360 is configured to rotatethe rotary piston assembly 310 in a first direction, e.g.,counter-clockwise, and the second actuation section 370 is configured torotate the rotary piston assembly 310 in a second directionsubstantially opposite the first direction, e.g., clockwise.

The rotary piston assembly 310 includes a linkage 380 connected to thejoint arm 260. A plurality of linkage arms 382 extend radially from thelinkage 380, the distal end of each linkage arm 382 including a bore 383substantially aligned with the axis of rotation of the rotary pistonassembly 310 and sized to accommodate one of a collection of connectorpins (not shown).

The first actuation section 360 includes a rotary piston 312, and thesecond actuation section 370 includes a rotary piston 314. While theexample actuator 300 includes two of the rotary pistons 312, 314, otherembodiments can include greater and/or lesser numbers of cooperative andopposing rotary pistons in various configurations. Examples of othersuch embodiments will be discussed below, for example, in thedescriptions of FIGS. 6A-11.

In the example rotary piston assembly 310 shown in FIG. 3, each of therotary pistons 312, 314 includes a piston end 316 and one or moreconnector arms 318. The piston end 316 is formed to have a body having agenerally semi-circular arc with substantially smooth surface. Each ofthe connector arms 318 includes a bore 384 substantially aligned withthe axis of the semi-circular arc of the piston end 316 and sized toaccommodate one of the connector pins (not shown).

The rotary pistons 312, 314 in the example rotary piston assembly 310 ofFIG. 3 are oriented to be rotationally opposite to each other. Therotary pistons 312 and 314 may be assembled to the linkage 380 byaligning the linkage arms 382 with the connector arms 318 such that thebores 383 align with the bores 384. The connector pins (not shown) maythen be inserted through the aligned bores 383, 384 to create hingedconnections between the pistons 312, 314 and the linkage 380. Eachconnector pin is slightly longer than the aligned bores. In the exampleassembly, about the circumferential periphery of each end of eachconnector pin that extends beyond the aligned bores is a circumferentialrecess (not shown) that can accommodate a retaining fastener (notshown), e.g., a snap ring or spiral ring.

The pressure chamber assembly 320 is removably connected to the jointarm 262 by a collection of fasteners (not shown) (e.g., bolts, pins,screws) that are passed through a collection of bores 370 in the jointarm 262 and into a collection of corresponding bores 371 in the axialends of the pressure chamber assembly 320. In the illustrated example,fluid pressure can be introduced to controllably urge the rotary pistons312, 314 out of the pressure chamber assembly 320. The movement of therotary pistons 312, 314, which are assembled to the linkage 380, canurge the joint arm 260 to pivot relative to the joint arm 262, which isassembled to the pressure chamber assembly 320.

The pressure chamber assembly 320 has a generally cylindrical shape.Referring back to FIG. 2, the joint 240 includes an outer housing 241configured as a tubular wall surrounding an interior bore sized toaccommodate the pressure chamber assembly 320. The outer housing 241 isconnected to, or is formed to be integral with, the linkage 380.

Returning to FIG. 3, the outer housing 241 (partly visible in FIG. 3)substantially surrounds the pressure chamber assembly 320. As the rotarypistons 312, 314 are actuated, the pressure chamber assembly 320, whichhas a generally cylindrical shape, rotates within the outer housing 241.The outer housing 241 provides a bearing surface that supports thepressure chamber assembly 320 as it rotates. In some embodiments,contact between the pressure chamber assembly 320 and the outer housing241 can bear a load. For example, a load on the joint arm 262 can betransmitted to the pressure chamber assembly 320, to the outer housing241 (e.g., through the bearing surface), to the linkage 380, and on tothe joint arm 260.

The joint arm 262 includes a circular seal groove 390, and the outerhousing 241 includes a corresponding seal groove 392. When the joint arm262 is mounted to the pressure chamber assembly 320, the seal groove 390and the seal groove 392 align. The seal grooves 390 and 392 accommodatea seal 394. The seals 394 substantially prevent external contaminants(e.g., dust, water, dirt, mud, sand) from entering the actuator 300,including the bearing surface between the outer housing 241 and thepressure chamber assembly 320 and including the rotary piston assembly310, as the joint arm 262 pivots relative to the outer housing 241. Insome implementations, the sealed arrangement of the actuator 300 canthus be used or submerged in wet, dirty, or other contaminatingenvironments substantially without exposing the internal components(e.g., the polished surfaces of the rotary pistons 312, 314) to externalcontamination.

FIG. 4 is a partial cutaway view of the example joint 250 of FIG. 2.FIG. 5 is an exploded view of the example joint 250. The joint 250includes a rotary piston actuator 400. In some embodiments, the rotarypiston actuator 400 can be the example rotary piston actuator 300 ofFIG. 3. In some embodiments, the rotary piston actuator 400 can be usedwith the multi-axis joint 200 of FIG. 2.

The actuator 400 includes the rotary piston assembly 310 and thepressure chamber assembly 320. The actuator 400 includes the firstactuation section 360 and a second actuation section 370. In the exampleof the actuator 400, the first actuation section 360 is configured torotate the rotary piston assembly 310 in a first direction, e.g.,counter-clockwise, and the second actuation section 370 is configured torotate the rotary piston assembly 310 in a second directionsubstantially opposite the first direction, e.g., clockwise.

The rotary piston assembly 310 of the actuator 400 includes a linkage480 connected to the joint arm 262. A plurality of linkage arms 482extend radially from the linkage 380, the distal end of each linkage arm482 including a bore 483 substantially aligned with the axis of rotationof the rotary piston assembly 310 and sized to accommodate one of acollection of connector pins (not shown).

The first actuation section 360 of the actuator 400 includes the rotarypiston 312, and the second actuation section 370 includes a rotarypiston 314. While the example actuator 300 includes two of the rotarypistons 312, 314, other embodiments can include greater and/or lessernumbers of cooperative and opposing rotary pistons in variousconfigurations. Examples of other such embodiments will be discussedbelow, for example, in the descriptions of FIGS. 6A-11.

The rotary pistons 312, 314 in the example rotary piston assembly 310 ofFIGS. 4 and 5 are oriented to be rotationally opposite to each other.The rotary pistons 312 and 314 may be assembled to the linkage 480 byaligning the linkage arms 482 with the connector arms 318 such that thebores 483 align with the bores 384. The connector pins (not shown) maythen be inserted through the aligned bores 483, 384 to create hingedconnections between the pistons 312, 314 and the linkage 480. Eachconnector pin is slightly longer than the aligned bores. In the exampleassembly, about the circumferential periphery of each end of eachconnector pin that extends beyond the aligned bores is a circumferentialrecess (not shown) that can accommodate a retaining fastener (notshown), e.g., a snap ring or spiral ring.

The pressure chamber assembly 320 of the actuator 400 is removablyconnected to the joint arm 264 by a collection of fasteners (not shown)(e.g., bolts, pins, screws) that are passed through a collection ofbores 470 in the joint arm 264 and into the collection of correspondingbores 371 in the axial ends of the pressure chamber assembly 320. In theillustrated example, fluid pressure can be introduced to controllablyurge the rotary pistons 312, 314 out of the pressure chamber assembly320. The movement of the rotary pistons 312, 314, which are assembled tothe linkage 480, can urge the joint arm 264 to pivot relative to thejoint arm 262, which is assembled to the pressure chamber assembly 320.

The pressure chamber assembly 320 of the actuator 400 has a generallycylindrical shape. Referring back to FIG. 2, the joint 250 includes anouter housing 251 configured as a tubular wall surrounding an interiorbore sized to accommodate the pressure chamber assembly 320. The outerhousing 251 is connected to, or is formed to be integral with, thelinkage 480.

Returning to FIG. 4, the outer housing 251 (partly visible in FIG. 4)substantially surrounds the pressure chamber assembly 320. As the rotarypistons 312, 314 are actuated, the pressure chamber assembly 320, whichhas a generally cylindrical shape, rotates within the outer housing 251.The outer housing 251 provides a bearing surface that supports thepressure chamber assembly 320 as it rotates. In some embodiments,contact between the pressure chamber assembly 320 and the outer housing251 can bear a load. For example, a load on the joint arm 264 can betransmitted to the pressure chamber assembly 320, to the outer housing251 (e.g., through the bearing surface), to the linkage 480, and on tothe joint arm 262.

The joint arm 264 includes a circular seal groove 390, and the outerhousing 251 includes a corresponding seal groove 492. When the joint arm264 is mounted to the pressure chamber assembly 320, the seal groove 390and the seal groove 492 align. The seal grooves 390 and 492 of theactuator 400 accommodate a seal 494. The seals 494 substantially preventexternal contaminants (e.g., dust, water, dirt, mud, sand) from enteringthe actuator 400, including the bearing surface between the outerhousing 251 and the pressure chamber assembly 320 and including therotary piston assembly 310, as the joint arm 264 pivots relative to theouter housing 251. In some implementations, the sealed arrangement ofthe actuator 400 can thus be used or submerged in wet, dirty, or othercontaminating environments substantially without exposing the internalcomponents (e.g., the polished surfaces of the rotary pistons 312, 314)to external contamination.

The rotary piston actuator 300 of FIG. 3 and the rotary piston actuatorof FIGS. 4-5 are examples of rotary piston actuators that can, in someembodiments, be used with the multi-axis joint 200 of FIG. 2. In someembodiments, various configurations of rotary piston actuators can beused. Several examples of such rotary piston actuators will be discussedin the descriptions of FIGS. 6A-11 below.

FIGS. 6A and 6B are sectional end and perspective views of an examplerotary piston actuator 600 having concentrically arranged pistons. Insome embodiments, the rotary piston actuator 600 can be the examplerotary piston actuator 300 of FIG. 3. In some embodiments, the rotarypiston actuator 600 can be used with the multi-axis joint 200 of FIG. 2.The actuator 600 includes rotary piston 610, a rotary piston 620, and apressure chamber assembly 630. While the example actuator 600 includestwo rotary pistons 610, 620, other embodiments can include greaterand/or lesser numbers of cooperative and opposing rotary pistons.

The housing 630 includes an arcuate chamber 631 having a cavity thatdefines an arc, illustrated by a line 633. The arc 633 extends in aplane between an open end 634 of the chamber 631 and an enclosed end 636of the chamber 631. The chamber 631 includes a fluid port (not shown) influid communication with the cavity. The arc 633 has a radius,illustrated by a line 635, in the plane. The radius 635 defines an axis638 perpendicular to the plane.

The housing 630 includes an arcuate chamber 650 having a cavity thatdefines an arc, illustrated by a line 653. The arc 653 extends in theplane between an open end 654 of the chamber 650 and an enclosed end 656of the chamber 650. The chamber 650 includes a fluid port (not shown) influid communication with the cavity. The arc 653 has a radius,illustrated by a line 655, radiating from the axis 638.

The radius 635 is greater than the radius 655, and the arc 633 has agreater diameter than the arc 653. The arcuate chamber 631 defines aspace that is substantially concentric with the arcuate chamber 650about the axis 638 in a substantially shared plane. In some embodiments,the arcuate chamber 631 can occupy an angular range about the axis 638that can at least partly overlap an angular range occupied by thearcuate chamber 650. In the illustrated example, the angular overlap isillustrated by an arc 660. As such, the arcuate chamber 631 and thearcuate chamber 650 are concentric about the axis 638, and in someembodiments, can occupy angularly overlapping ranges about the axis 638,substantially without intersecting each other. In other words, thearcuate chamber 631 and the arcuate chamber 650 are formed as twosections of two rings, where the two rings have two different diameterssuch that the chambers 631, 650 do not intersect each other, and the twosections can at least partly co-occupy a range of angles about the axis638 without the chambers 631, 650 intersecting each other.

In the example rotary piston actuator 600 shown in FIGS. 6A and 6B, therotary piston 610 includes a piston end 612 and a contact end 614. Therotary piston 620 includes a piston end 622 and a contact end 624. Thepiston ends 612 and 622 are formed to have a generally geometric bodyhaving a substantially smooth surface. The contact ends 614 and 624 areconfigured to contact (e.g., push, urge) a rotor arm 640.

The piston end 622 has an arcuate shape that is configured to fit withinthe arcuate chamber 631. The piston end 622 is disposed within thehousing 630 for reciprocal movement within the arcuate chamber 631, inthe plane through the open end 634. A seal 672, the cavity, and thepiston end 622 define another pressure chamber, and the contact end 624is oriented to contact the rotor arm 640.

The piston end 612 has an arcuate shape that is configured to fit withinthe arcuate chamber 650. The piston end 612 is disposed within thehousing 630 for reciprocal movement within the arcuate chamber 650, inthe plane through the open end 654. A seal 670, the cavity, and thepiston end 612 define a pressure chamber, and the contact end 614 isoriented to contact the rotor arm 640.

The rotary piston 610 in the example actuator 600 of FIGS. 6A-6B isoriented in rotationally opposite relative to the rotary piston 620, andthe piston end 612 and the piston end 622 contact angularly oppositesides of the rotor arm 640.

The rotor arm 640 is removably connected to an inner surface 682 of atubular rotor assembly 680. The rotor assembly 680 substantiallysurrounds the housing 630. An arcuate actuation space 690 is definedbetween the inner surface 682 and the housing 630, and between aterminal end 692 and a terminal end 694. The open end 634 is formed inthe terminal end 692, and the open end 654 is formed in the terminal end694.

As fluid pressure is applied to the arcuate chamber 631, the piston end622 is urged outward from the arcuate chamber 631. As the arcuate piston620 moves, the contact end 624 contacts the rotor arm 640, which isremovably connected to the rotor assembly 680, to urge rotationalmovement of the rotor assembly 680 about the axis 638. In theillustrated example, this pressurization would cause the arcuate piston620, the rotor arm 640, and the rotor assembly 680 to revolvecounterclockwise about the axis 638.

As fluid pressure is applied to the arcuate chamber 650, the piston end612 is urged outward from the arcuate chamber 650. As the arcuate piston610 moves, the contact end 614 contacts the rotor arm 640, which isremovably connected to the rotor assembly 680, to urge rotationalmovement of the rotor assembly 680 about the axis 638. In theillustrated example, this pressurization would cause the arcuate piston610, the rotor arm 640, and the rotor assembly 680 to revolve clockwiseabout the axis 638.

In some embodiments, a configuration of concentric, non-intersecting,and angularly overlapping chambers 631 and 650 can provide an extendedrange of actuation. In the illustrated example, the arcuate actuationspace 690 occupies an approximately 180° arc. As such, the rotorassembly 680 can be actuated relative to the housing 630, through an archaving a range of zero to approximately 180°, e.g., 180° minus anangular space based on the angular thicknesses of the contact ends 614and 624 and the rotor arm 640 within the arcuate actuation space, whichcan vary by application.

In some embodiments, rotary piston actuator 600 can be used to pivotallyconnect and actuate a joint. For example, the housing 630 can beconnected to a first arm portion or mounting point of a machine, and therotor assembly 680 can be a connected to a second arm portion ormounting point on the machine, to actuate the first arm portion ormounting point relative to the second. In some embodiments, the rotarypiston actuator 600 can be the rotary piston actuator 300 or 400 ofFIGS. 3-5. For example, the housing 630 can be the pressure chamberassembly 320, removably connected to the joint arm 262, and the rotorassembly 680 can be the outer housing 241 removably connected to orformed integral with the joint arm 260.

The example rotary piston actuator 600 also includes a bore 695 formedsubstantially along the axis 683. In some implementations, one or moreof the arcuate chambers 631, 650 can be in fluid communication with thebore 695 through one or more fluid ports (not shown). For example, fluidpressure can be applied to the bore 695 to pressurize the chamber 631and urge counterclockwise movement of the rotor assembly 680. In anotherexample, the rotor assembly 680 can be rotated clockwise, urging thepiston end 622 into the chamber 631, pressurizing fluid in the chamber631 and urging the fluid out through the port to the bore 695. In someembodiments, the bore 695 may accommodate a fluid delivery shaftconfigured to provide a portion of a fluid circuit between one or bothof the chambers 631, 650 (e.g., through the fluid ports) and fluidsupplies outside of the actuator 600 (e.g., a fluid pump or reservoir).

FIGS. 7A and 7B are sectional end and perspective views of an examplerotary piston actuator 700 with spatially co-located (e.g., nested)pistons. In some embodiments, the rotary piston actuator 700 can be theexample rotary piston actuator 300 of FIG. 3. In some embodiments, therotary piston actuator 700 can be used with the multi-axis joint 200 ofFIG. 2. The actuator 700 includes rotary piston 710, a rotary piston720, and housing 730. While the example actuator 700 includes two rotarypistons 710, 720, other embodiments can include greater and/or lessernumbers of cooperative and opposing rotary pistons.

The actuator 700 includes a housing 730. The housing 730 includes anarcuate chamber housing 731 defining an arcuate chamber having a cavityformed as a ring-shaped segment along an arc, illustrated by a line 733.The arc 733 extends in a plane between an open end 734 of the chamber731 and an enclosed end 736 of the chamber housing 731. The chamberhousing 731 includes a fluid port (not shown) in fluid communicationwith the cavity. The arc 733 has a central radius, illustrated by a line735, in the plane. The radius 735 defines an axis 738 perpendicular tothe plane.

The ring-shaped segment defined by the chamber housing 731 has an outerradius 701 in the plane. The radius 735 also defines the axis 738 andextends perpendicular to the plane. The ring-shaped segment defined bythe chamber housing 731 also has an inner radius 702 in the plane.

The housing 730 includes an arcuate chamber 750. The arcuate chamber 750has an inner chamber wall 704 that defines a cavity formed as anotherring-shaped segment formed along the arc 733 in the plane. The chamber750 extends between an open end 754 and an enclosed end 756. The chamber750 includes fluid port (not shown) in fluid communication with thecavity defined by the chamber 750. The ring-shaped segment defined bythe chamber 750 has an outer radius 706 that extends from the axis 738.The outer radius 706 is larger than the outer radius 701 and isconcentric with the outer radius 701 about the axis 738 in the plane.The ring-shaped segment defined by the chamber 750 also has an innerradius 707 that is smaller than the inner radius 702 and is concentricwith the inner radius 702 about the axis 738 in the plane. Thering-shaped segment defined by the chamber 750 also has a central radius737 that is substantially the same as the central radius 735

The arcuate chamber 750 is oriented rotationally opposite to the arcuatechamber housing 731 about the axis 738. The arcuate chamber housing 731defines a space that is substantially concentric with the arcuatechamber 750 about the arc 733 in a substantially shared plane. At leasta portion of the chamber housing 731 is enclosed within at least aportion of the chamber 750 in the plane. This arrangement of the chamberhousing 731 concentrically within the chamber 750 defines an arcuatetubular space 721 between the arcuate chamber housing 731 and the innerchamber wall 704.

In some embodiments, the arcuate chamber housing 731 can occupy anangular range about the axis 738 that can at least partly overlap anangular range occupied by the arcuate chamber 750. In the illustratedexample, the angular overlap is illustrated by an arc 760. As such, thearcuate chamber housing 731 is nested within the arcuate chamber 750along a portion of the axis 738, and in some embodiments, can occupyangularly overlapping ranges about the axis 738, substantially withoutbeing in fluid communication each other.

In the example rotary piston actuator 700 shown in FIGS. 7A and 7B, therotary piston 710 includes a piston end 712 and a contact end 714. Therotary piston 720 includes a piston end 722 and a contact end 724. Thecontact ends 614 and 624 are configured to contact (e.g., push, urge) arotor arm 740.

The piston end 712 is formed to have a generally geometric body having asubstantially smooth surface. The piston end 712 has an arcuate shapethat is configured to fit within the arcuate chamber of the arcuatechamber housing 731. The piston end 712 is disposed within the housing730 for reciprocal movement within the arcuate chamber of the arcuatechamber housing 731, in the plane through the open end 734. A seal 770,the cavity, and the piston end 712 define a pressure chamber, and thecontact end 714 is oriented to contact the rotor arm 740.

The piston end 722 has an arcuate tubular shape that is configured tofit within the arcuate chamber 750. The piston end 722 is disposedwithin the housing 730 for reciprocal movement within the arcuatetubular space 721 between the arcuate chamber housing 731 and the innerchamber wall 704, in the plane through the open end 754. A seal 772, thecavity, and the piston end 722 define another pressure chamber, and thecontact end 724 is oriented to contact the rotor arm 740.

The rotary piston 710 in the example actuator 700 of FIGS. 7A-7B isoriented in rotationally opposite relative to the rotary piston 720, andthe piston end 712 and the piston end 722 contact angularly oppositesides of the rotor arm 740.

The rotor arm 740 is removably connected to an inner surface 782 of atubular rotor assembly 780. The rotor assembly 780 substantiallysurrounds the housing 730. An arcuate actuation space 790 is definedbetween the inner surface 782 and the housing 730, and between aterminal end 792 and a terminal end 794. The open end 734 is formed inthe terminal end 794, and the open end 754 is formed in the terminal end792.

As fluid pressure is applied to the arcuate chamber 731, the piston end712 is urged outward from the arcuate chamber 731. As the arcuate piston710 moves, the contact end 714 contacts the rotor arm 740, which isremovably connected to the rotor assembly 780, to urge rotationalmovement of the rotor assembly 780 about the axis 738. In theillustrated example, this pressurization would cause the arcuate piston710, the rotor arm 740, and the rotor assembly 780 to revolve clockwiseabout the axis 738.

As fluid pressure is applied to the arcuate chamber 750, the piston end722 is urged outward from the arcuate chamber 750. As the arcuate piston720 moves, the contact end 724 contacts the rotor arm 740, which isremovably connected to the rotor assembly 780, to urge rotationalmovement of the rotor assembly 780 about the axis 738. In theillustrated example, this pressurization would cause the arcuate piston720, the rotor arm 740, and the rotor assembly 780 to revolvecounterclockwise about the axis 738.

In some embodiments, a configuration of substantially coaxial, nestedchambers, such as the arcuate chamber housing 731 within the arcuatechamber 750 can provide an extended range of actuation. In theillustrated example, the arcuate actuation space 790 occupies anapproximately 180° arc. As such, the rotor assembly 780 can be actuatedrelative to the housing 730, through an arc having a range of zero toapproximately 180°, e.g., 180° minus an angular space based on theangular thicknesses of the contact ends 714 and 724 and the rotor arm740 within the arcuate actuation space, which can vary by application.

In some embodiments, rotary piston actuator 700 can be used to pivotallyconnect and actuate a joint. For example, the housing 730 can beconnected to a first arm portion or mounting point of a machine, and therotor assembly 780 can be a connected to a second arm portion ormounting point on the machine, to actuate the first arm portion ormounting point relative to the second. In some embodiments, the rotarypiston actuator 700 can be the rotary piston actuator 300 or 400 ofFIGS. 3-5. For example, the housing 730 can be the pressure chamberassembly 320, removably connected to the joint arm 262, and the rotorassembly 780 can be the outer housing 241 removably connected to orformed integral with the joint arm 260.

The example rotary piston actuator 700 also includes a bore 795 formedsubstantially along the axis 783. In some implementations, one or moreof the arcuate chamber of the arcuate chamber housing 731 and thearcuate chamber 750 can be in fluid communication with the bore 795through one or more fluid ports (not shown). For example, fluid pressurecan be applied to the bore 795 to pressurize the chamber 750 and urgecounter-clockwise movement of the rotor assembly 780. In anotherexample, the rotor assembly 780 can be rotated clockwise, urging thepiston end 722 into the chamber 750, pressurizing fluid in the chamber750 and urging the fluid out through the port to the bore 795. In someembodiments, the bore 795 may accommodate a fluid delivery shaftconfigured to provide a portion of a fluid circuit between one or bothof the chamber in the chamber housing 731 and the chamber 750 (e.g.,through the fluid ports) and fluid supplies outside of the actuator 700(e.g., a fluid pump or reservoir).

FIGS. 8A and 8B are sectional views of an example rotary piston actuator(RPA) 800 with multi-chamber pistons. In general, the rotary pistonactuator 800 is configured as an RPA-within-an-RPA. In general, an RPAcan be configured to have a piston that is hollow so as to act as apressure chamber for a second piston within the hollow piston. In suchan example, the hollow piston separates two independent pressurechambers that can be actuated individually, for example to provide twodifferent torques, or to provide coarse and fine positioning control. Insome embodiments, the rotary piston actuator 800 can be the examplerotary piston actuator 300 of FIG. 3. In some embodiments, the rotarypiston actuator 800 can be used with the multi-axis joint 200 of FIG. 2.

The actuator 800 includes a piston assembly 810, a piston assembly 820,and a pressure chamber assembly 860 (e.g., a housing). The pressurechamber assembly 860 defining a chamber including a cavity 862 a, afirst fluid port (not shown) in fluid communication with the cavity 862a, and an open end 864 a. The pressure chamber assembly 860 also definesa chamber including a cavity 862 b, a fluid port (not shown) in fluidcommunication with the cavity 862 b, and an open end 864 b.

The piston assembly 820 includes a tubular piston 822 a. The tubularpiston 822 a defines a chamber including a cavity 824 a and an open end826 a. A fluid port (not shown) is in fluid communication with thecavity 824 a. The tubular piston 822 a is disposed in the pressurechamber assembly 860 for reciprocal movement in the chamber 862 athrough the open end 864 a. A seal 866 a, the cavity 824 a, and thepiston 822 a define a pressure chamber 868 a.

The piston assembly 820 includes a tubular piston 822 b. The tubularpiston 822 b defines a chamber including a cavity 824 b and an open end826 b. A fluid port (not shown) is in fluid communication with thecavity 824 b. The tubular piston 822 b is disposed in the pressurechamber assembly 860 for reciprocal movement in the chamber 862 bthrough the open end 864 b. A seal 866 b, the cavity 824 b, and thepiston 822 b define a pressure chamber 868 b.

The piston assembly 810 includes a piston 812 a disposed in the pistonassembly 820 for reciprocal movement in the chamber 868 a through theopen end 864 a. A seal 826 a, the cavity 824 a, and the piston 812 adefine a pressure chamber 828 a. A portion 814 a of the piston 812 acontacts a rotor arm 870 (e.g., an end effector).

The piston assembly 810 includes a piston 812 b disposed in the pistonassembly 820 for reciprocal movement in the chamber 868 b through theopen end 864 b. A seal 826 b, the cavity 824 b, and the piston 812 bdefine a pressure chamber 828 b. A portion 814 b of the piston 812 bcontacts the rotor arm 870 (e.g., an end effector).

In the example of the actuator 800, the pressure chambers 828 a, 828 b,868 a, and 868 b are substantially sealed from each other and can bepressurized individually. For example, a fluid pressure may be appliedto the pressure chamber 828 a and a different fluid pressure may beapplied to the pressure chamber 828 b.

In the example of the actuator 800, the pressure chamber 828 a isconfigured to rotate the rotary piston assembly 810 in a firstdirection, e.g., clockwise, and the pressure chamber 828 b is configuredto rotate the rotary piston assembly 810 in a second directionsubstantially opposite the first direction, e.g., counter-clockwise.

In the example of the actuator 800, the pressure chamber 868 a isconfigured to rotate the rotary piston assembly 820 in a firstdirection, e.g., clockwise, and the pressure chamber 868 b is configuredto rotate the rotary piston assembly 820 in a second directionsubstantially opposite the first direction, e.g., counter-clockwise.

In some embodiments, a configuration of nested, individuallypressurizable chambers 828 a, 828 b, 868 a, and 868 b can provide anextended range of actuation. In the illustrated example, the chambers828 a, 828 b, 868 a, and 868 b each provide approximately 90° ofrotation. However, the cooperative combination of the chambers 828 a and868 a can provide approximately 180° of rotation. Similarly, thecooperative combination of the chambers 828 b and 868 b can provideapproximately 180° of rotation in the opposite direction. As such, therotor arm 860 can be actuated relative to the housing 830, through anarc having a range of zero to approximately 180°, which can vary byapplication.

In some embodiments, rotary piston actuator 800 can be used to pivotallyconnect and actuate a joint. For example, the housing 830 can beconnected to a first arm portion or mounting point of a machine, and theend effector 870 can be a connected to a second arm portion or mountingpoint on the machine, to actuate the first arm portion or mounting pointrelative to the second. In some embodiments, the rotary piston actuator800 can be the rotary piston actuator 300 or 400 of FIGS. 3-5. Forexample, the housing 830 can be the pressure chamber assembly 320,removably connected to the joint arm 262, and the end effector 870 canbe the outer housing 241 removably connected to or formed integral withthe joint arm 260.

FIG. 9 is an exploded view of an example rotary piston actuator jointportion 901. In some embodiments, the joint 901 can be used with themulti-axis joint 200 of FIG. 2, wherein the rotary piston actuator 400has been replaced by a modular rotary piston actuator 900. In general,the modular rotary piston actuator 900 includes one or more rotarypiston actuator modules, such as the examples of the actuators 600, 700,and 800 discussed in the descriptions of FIGS. 6A-8B.

The actuator 900 includes three rotary piston actuator modules 902 a-902c. Generally speaking, the rotary piston actuator modules 902 a-902 care individually replaceable and are generally interchangeable withinthe modular rotary piston actuator 900. In some embodiments, each of themodules 902 a-902 c can be an embodiment of any one of the rotary pistonactuators 300, 400, 600, 700, or 800 of FIGS. 3-8B, or any otherappropriate rotary piston actuator, rotary vane actuator, orcombinations thereof.

The rotary piston actuator modules 902 a-902 c each include a rotarypiston assembly 910 (e.g., the rotary piston assemblies 310, 810, 820,the rotary pistons 610, 620, 710, 720) and a housing 920 which alsoserves as a pressure chamber assembly (e.g., the pressure chamber 320,the pressure chamber assemblies 630, 730, 860).

The rotary piston assemblies 910 each includes a linkage 980 (e.g.,connectable to the joint arm 260). A plurality of linkage arms 982extend radially from the linkage 980, the distal end of each linkage arm982 including a bore 983 substantially aligned with the axis of rotationof the rotary piston assembly 910 and sized to accommodate one of acollection of connector pins (not shown). While the example actuator 900includes three of the modules 902 a-902 c, other embodiments can includegreater and/or lesser numbers of cooperative and opposing rotary pistonsactuator modules in various configurations.

Each of the example rotary piston assemblies 910 shown in FIG. 9,includes a rotary piston 912. Each of the rotary pistons 912 includes apiston end 916 and one or more connector arms 918. The piston ends 916are formed to have bodies having a generally semi-circular arcs withsubstantially smooth surfaces. Each of the connector arms 918 includes abore 984 substantially aligned with the axis of the semi-circular arc ofits respective piston end 916 and sized to accommodate one of theconnector pins (not shown).

The pressure chamber assemblies 920 have a generally cylindrical shape.The linkage 980 includes an outer housing 941 configured as a tubularwall surrounding an interior bore sized to accommodate the pressurechamber assemblies 920. The outer housing 941 is connected to, or isformed to be integral with, the linkage 980.

The rotary piston actuator modules 902 a-902 c are removably assembledby inserting them axially into the outer housing 941. The rotary pistonactuator modules 902 a-902 c are interlinked rotationally by acollection of pegs 951 and corresponding recesses (not shown) formedupon the axial faces of the pressure chamber assemblies 920. The rotarypiston actuator modules 902 a-902 c are also interlinked rotationally bya collection of rods 952 inserted through a collection of bores 970formed in the axially through the pressure chamber assemblies 920.

Each of the pressure chamber assemblies 920 includes a central bore 995.A fluid delivery shaft 954 is arranged axially within the central bores995. The fluid delivery shaft 954 is discussed further in thedescriptions of FIGS. 10 and 11.

Each of the rotary piston actuator modules 902 a-902 c is configured tobe removably assembled into the actuator 900 in two differentoperational orientations. In the illustrated example, the rotary pistonactuator modules 902 a and 902 c are oriented to be rotationallycooperative with each other. The rotary piston actuator module 902 b isoriented to be rotationally opposite to the rotary piston actuatormodules 902 a and 902 c. In some embodiments, the rotary piston actuatormodules 902 a-902 c can be assembled into the actuator 900 in a selectedone of both clockwise and counter-clockwise orientations. In someembodiments, clockwise and counter-clockwise combinations of the rotarypiston actuator modules 902 a-902 c can be assembled (e.g., axiallyarranged) into the actuator 900 in substantially any appropriate order.

While three of the rotary piston actuator modules 902 a-902 c are shownand described with respect to FIG. 9, in some embodiments the actuator900 may implement greater or fewer numbers of rotary piston actuatormodules. In some embodiments, greater numbers of the rotary pistonactuator modules 902 a-902 c may be oriented in one rotational directionthan the other. For example, the actuator 900 may be used in anexcavator arm in which greater operational torques may be needed forlifting operations (e.g., “up” or “clockwise” rotation) than diggingoperations (e.g., “down” or “counter-clockwise” rotation). In such anexample, the rotary piston actuator modules 902 a-902 c may be purposelyarranged to provide an asymmetrical torque that reflects the desiredoperational torques.

In some embodiments, the capability to configure the actuator 900 withasymmetrical torque capabilities that reflect the application to whichthe actuator 900 is to be applied can improve the overallpower-to-weight ratio, improve the torque-to-weight, and/or reduce thevolume of space of the actuator 900. For example, a symmetricalapplication may require the use of two rotary piston actuator modules ina clockwise configuration and two rotary piston actuator modules in acounter-clockwise configuration (e.g., four total), whereas anasymmetrical application may only require the use of two rotary pistonactuator modules in the clockwise configuration and one rotary pistonactuator module in the counterclockwise (e.g., three total). In theexample of the asymmetrical application, the space, power consumption,and expense associated with the fourth rotary piston actuator module maybe avoided.

Furthermore, the assembly 900 may be reconfigured as needed to alter itsasymmetric characteristics. For example, an excavator that originallyconfigured to provide more lifting power than digging power for one setof tasks can be reconfigured to provide more digging power than liftingpower for a different set of tasks by re-arranging or replacing therotary piston actuator modules 902 a-902 c in the actuator 900.

The rotary pistons 912 may be assembled to the linkage 980 by aligningthe linkage arms 982 with the connector arms 918 such that the bores 983align with the bores 984. The connector pins (not shown) may then beinserted through the aligned bores 983, 984 to create hinged connectionsbetween the pistons 912 and the linkage 980. Each connector pin isslightly longer than the aligned bores. In the example assembly, aboutthe circumferential periphery of each end of each connector pin thatextends beyond the aligned bores is a circumferential recess (not shown)that can accommodate a retaining fastener (not shown), e.g., a snap ringor spiral ring.

The pressure chamber assemblies 920 are removably connected to the jointarm 964 by a collection of fasteners (not shown) (e.g., bolts, pins,screws) that are passed through the collection of bores 970 in the jointarm 964 and into a collection of corresponding bores 971 in the axialends of the pressure chamber assemblies 920. In the illustrated example,fluid pressure can be introduced to controllably urge the rotary pistons912 out of the pressure chamber assemblies 920. The movement of therotary pistons 912 which are assembled to the linkage 980, can urge thelinkage 980 to pivot relative to the joint arm 964, which is assembledto the pressure chamber assemblies 920.

The outer housing 941 substantially surrounds the pressure chamberassemblies 920. As the rotary pistons 912 are actuated, the pressurechamber assemblies 920, which have a generally cylindrical shape, rotatewithin the outer housing 941. The outer housing 941 provides a bearingsurface that supports the pressure chamber assemblies 920 as theyrotate. In some embodiments, contact between the pressure chamberassemblies 920 and the outer housing 941 can bear a load. For example, aload on the joint arm 964 can be transmitted to the pressure chamberassemblies 920, to the outer housing 941 (e.g., through the bearingsurface), and on to the linkage 980.

The joint arm 964 includes a circular seal groove 990, and the outerhousing 991 includes a corresponding seal groove 992. When the joint arm964 is mounted to the pressure chamber assemblies 920, the seal groove990 and the seal groove 992 align. The seal grooves 990 and 992accommodate a collection of seals 994. The seals 394 substantiallyprevent external contaminants (e.g., dust, water, dirt, mud, sand) fromentering the actuator 900, including the bearing surface between theouter housing 941 and the pressure chamber assembly 920 and includingthe rotary piston assemblies 910, as the joint arm 964 pivots relativeto the outer housing 941. In some implementations, the sealedarrangement of the actuator 900 can thus be used or submerged in wet,dirty, or other contaminating environments substantially withoutexposing the internal components (e.g., the polished surfaces of therotary pistons 912) to external contamination.

In some embodiments, the assembly 900 may include internal gearingbetween the pressure chamber assemblies 920 and the joint arm 964. Forexample, the assembly 900 may include a gear module that has a shapewhich is similar to those of the rotary piston actuator modules 902a-902 c and can be assembled between the rotary piston actuator modules902 a-902 c and the joint art 964 to modify the amount of torque orrange of motion between the rotary piston actuator modules 902 a-902 cand the joint art 964. In some embodiments, the gear module can be aplanetary gear module.

In some embodiments, the assembly 900 may include internal braking orclutching. For example, the assembly 900 may include a clutch modulethat has a shape which is similar to those of the rotary piston actuatormodules 902 a-902 c and can be assembled into the assembly 900 toprovide a load holding capability. In some embodiments, a gear modulemay include features that can controllably interfere with gear movementto provide clutching or braking control.

In some embodiments, the linkage arms 982 and the piston ends 912 mayinclude anti-rotation features. For example, the linkage arms 982 mayinclude extensions that intermesh rotationally about the bores 983, 984with corresponding extensions of the piston ends 912. Such intermeshingextensions can prevent separation of the linkage arms 982 from thepiston ends 912 (e.g., in the event of a break in the interconnectingrod). Such intermeshing can prevent rotation of the pistons 910 relativeto the linkage arms 982 and reduce loading placed upon seals within thepressure chamber assemblies 920.

FIG. 10 is a sectional view of an example fluid delivery shaft 1000. Insome embodiments, the fluid delivery shaft 1000 can be the example fluiddelivery shaft 954 of FIG. 9. The fluid delivery shaft 1000 is shown asbeing arranged axially through the central bores 1003 of a collection ofmodular rotary piston actuators 1002 a-1002 c (e.g., the modular rotarypiston actuators 902 a-902 c). Each of the modular rotary pistonactuators 1002 a-1002 c includes a fluid port 1005 in communication witha pressure chamber 1007.

A fluid path 1010 a and a fluid path 1010 b are formed within the fluiddelivery shaft 1000. The fluid path 1010 a extends between a pair ofterminal fluid ports 1012 a formed near the axial ends of the fluiddelivery shaft 1000 and a collection of axial fluid ports 1014 a formedalong the periphery of the fluid delivery shaft 1000. Each axial fluidport 1014 a substantially aligns with a corresponding one of the modularrotary piston actuators 1002 a-1002 c.

The fluid path 1010 b extends between a pair of terminal fluid ports1012 b formed near the axial ends of the fluid delivery shaft 1000 and acollection of axial fluid ports 1014 b formed along the periphery of thefluid delivery shaft 1000. Each axial fluid port 1014 b substantiallyaligns with a corresponding one of the modular rotary piston actuators1002 a-1002 c, radially opposite from a corresponding axial fluid port1014 a.

A collection of seals 1016 are arranged about the periphery of the fluiddelivery shaft 1000. Each of the fluid ports 1005 and correspondingopposing pairs of axial fluid ports 1014 a and 1014 b have a seal 1016 aarranged on a first side axial side of the fluid ports 1005 and theaxial fluid ports 1014 a and 1014 b along the length of the fluiddelivery shaft 1000, and have a seal 1016 b on a second, opposite axialside of the fluid ports 1005 and the axial fluid ports 1014 a and 1014 balong the length of the fluid delivery shaft 1000.

For each of the modular rotary piston actuators 1002 a-1002 c, the bore1003, the seal 1016 a, the seal 101 b, and the fluid delivery shaft 1000define a fluid delivery chamber 1020. This arrangement creates a fluidcircuit that can connect the axial fluid ports 1014 a and 1014 b to thepressure chambers 1007 through the fluid ports 1005. As such, theterminal fluid ports 1012 a, 1012 b are in fluid communication with thepressure chambers 1007.

Each of the modular rotary piston actuators 1002 a-1002 c can beassembled about the fluid delivery shaft 1000 in two arrangements (e.g.,clockwise and counter-clockwise). In the illustrated example, themodular rotary piston actuators 1002 a and 1002 c are assembled in afirst orientation and the modular rotary piston actuator 1002 b isassembled in an opposite orientation. A collection of plugs 1030 can beinserted into selected ones of the axial fluid ports 1014 a and 1014 bto select which of the fluid paths 1011 a, 1011 b provides fluid to thechambers 1007. In the illustrated example, the ports 1014 b of themodular rotary piston actuators 1002 a and 1002 c are blocked by theplugs 1030, and the port 1014 a of the modular rotary piston actuator1002 b. In the illustrated configuration, the fluid path 1011 a can bepressurized to provide fluid to the modular rotary piston actuators 1002a and 1002 c to urge rotation in a first direction, and the fluid path1011 b can be pressurized to provide fluid to the modular rotary pistonactuator 1002 b to urge rotation in an opposite direction.

FIG. 11 is a sectional view of an example fluid delivery shaft 1100. Insome embodiments, the fluid delivery shaft 1100 can be the example fluiddelivery shaft 954 of FIG. 9. The fluid delivery shaft 1100 is shown asbeing arranged axially through the central bores 1103 of a collection ofmodular rotary piston actuators 1102 a-1102 c (e.g., the modular rotarypiston actuators 902 a-902 c). Each of the modular rotary pistonactuators 1102 a-1102 c includes a fluid port 1105 in communication witha pressure chamber 1107.

A fluid path 1110 a and a fluid path 1110 b are formed within the fluiddelivery shaft 1100. The fluid path 1110 a extends between a pair ofterminal fluid ports 1112 a formed near the axial ends of the fluiddelivery shaft 1100 and a collection of axial fluid ports 1114 a formedalong the periphery of the fluid delivery shaft 1100. Each axial fluidport 1114 a substantially aligns with a corresponding one of the modularrotary piston actuators 1102 a-1102 c.

The fluid path 1110 b extends between a pair of terminal fluid ports1112 b formed near the axial ends of the fluid delivery shaft 1100 and acollection of axial fluid ports 1114 b formed along the periphery of thefluid delivery shaft 1100. Each axial fluid port 1114 b substantiallyaligns with a corresponding one of the modular rotary piston actuators1102 a-1102 c, radially opposite from a corresponding axial fluid port1114 a.

A collection of seals 1116 are arranged about the periphery of the fluiddelivery shaft 1100. Each of the fluid ports 1105 and correspondingpairs of axial fluid ports 1114 a and 1114 b have a seal 1116 a arrangedon a first side axial side of the fluid ports 1105 and the axial fluidports 1114 a and 1114 b along the length of the fluid delivery shaft1100, and have a seal 1116 b on a second, opposite axial side of thefluid ports 1105 and the axial fluid ports 1114 a and 1014 b along thelength of the fluid delivery shaft 1100. A third seal 1116 c is arrangedsubstantially centered between each pair of seals 1116 a and 1116 b.

For each of the modular rotary piston actuators 1002 a-1002 c, the bore1003, the seal 1116 a, the seal 111 b, and the fluid delivery shaft 1100define a fluid delivery chamber 1120 a, and the seal 1116 c, the seal111 b, and the fluid delivery shaft 1100 define a fluid delivery chamber1120 b. This arrangement creates a fluid circuit that can connect theaxial fluid ports 1114 a and 1114 b to the pressure chambers 1107through the fluid ports 1105. As such, the terminal fluid ports 1112 a,1112 b are in fluid communication with the pressure chambers 1107.

Each of the modular rotary piston actuators 1102 a-1102 c can beassembled about the fluid delivery shaft 1100 in two arrangements (e.g.,clockwise and counter-clockwise). In the illustrated example, themodular rotary piston actuators 1102 a and 1102 c are assembled in afirst orientation and the modular rotary piston actuator 1102 b isassembled in an opposite orientation.

The fluid port 1105 in each of the modular rotary piston actuators 1102a-1102 c is offset axially away from the center of the pressure chamberalong the bore 1103. As such, the fluid port 1105 will be closer to aproximal end of the fluid delivery shaft 1100 and further away from thedistal end when assembled to the fluid delivery shaft 1100 in a firstorientation, and the fluid port 1105 will be relatively further awayfrom the proximal end and relatively closer to the distal end in theopposite orientation.

When assembled about the fluid delivery shaft 1100, and depending on theorientation of the modular rotary piston actuators 1102 a-1102 c, thefluid ports 1105 will be aligned between either the seal 1116 a and theseal 1116 c, or between the seal 1116 b and the seal 1116 c. As such,depending on the orientation of the modular rotary piston actuators 1102a-1102 c, either the fluid delivery chambers 1120 a will fluidly connectthe fluid path 1111 a with the chambers 1107, or the fluid deliverychambers 1120 b will fluidly connect the fluid path 1111 b with thechambers 1107. In the illustrated example, the fluid ports 1105 of themodular rotary piston actuators 1102 a and 1102 c are aligned with thefluid delivery chambers 1120 a, and the port 1105 of the modular rotarypiston actuator 1102 b is aligned with the fluid delivery chamber 1120b. In the illustrated configuration, the fluid path 1111 a can bepressurized to provide fluid to the modular rotary piston actuators 1102a and 1102 c to urge rotation in a first direction, and the fluid path1111 b can be pressurized to provide fluid to the modular rotary pistonactuator 1102 b to urge rotation in an opposite direction.

FIG. 12 is a flow diagram of an example process 1200 for performingrotary actuation. In some implementations, the process 1200 can beperformed by the rotary piston-type actuators 300, 400, 600, 700, 800,900, 1002 a-1002 c, and/or 1102 a-1102 c of FIGS. 3-11.

At 1210, a rotary actuator is provided. The rotary actuator of exampleactuator 1200 includes a first housing defining a first arcuate chamberincluding a first cavity, a first fluid port in fluid communication withthe first cavity, an open end, and a first seal disposed about aninterior surface of the open end, a rotor arm extending radiallyoutward, and an arcuate-shaped first piston disposed in the firsthousing for reciprocal movement in the first arcuate chamber through theopen end. The first seal, the first cavity, and the first piston definea first pressure chamber. For example, the actuator 600 includes thecomponents of the pressure chamber assembly 630 and the rotary piston610.

At 1220, a pressurized fluid is applied to the first pressure chamber.For example, pressurized fluid can be flowed through the fluid port (notshown) into the pressure chamber 650.

At 1230, the first piston is urged partially outward from the firstpressure chamber to urge rotation of the rotor arm in a first direction.For example, a volume of pressurized fluid flowed into the pressurechamber 650 will displace a similar volume of the rotary piston 610,causing the rotary piston 610 to be partly urged out of the pressurechamber 650, which in turn will cause the rotor arm 640 to rotateclockwise.

At 1240, the rotary output shaft is rotated in a second directionopposite that of the first direction. For example, the rotor arm 640 canbe rotated counter-clockwise by an external force, such as anothermechanism, a torque-providing load, a return spring, or any otherappropriate source of rotational torque.

At 1250, the first piston is urged partially into the first pressurechamber to urge pressurized fluid out the first fluid port. For example,the rotary piston 610 can be pushed into the pressure chamber 650, andthe volume of the piston end 612 extending into the pressure chamber 650will displace a similar volume of fluid, causing it to flow out thefluid port (not shown).

In some embodiments, the example process 100 can be used to providesubstantially constant power over stroke to a connected mechanism. Forexample, as the actuator 600 rotates, there may be substantially littleposition-dependent variation in the torque delivered to a connectedload.

In some embodiments, the first housing further defines a second arcuatechamber including a second cavity, a second fluid port in fluidcommunication with the second cavity, and a second seal disposed aboutan interior surface of the open end, the rotor assembly also includes asecond rotor arm, the rotary actuator also includes an arcuate-shapedsecond piston disposed in said housing for reciprocal movement in thesecond arcuate chamber, wherein the second seal, the second cavity, andthe second piston define a second pressure chamber, and a secondconnector coupling a first end of the second piston to the second rotorarm. For example, the actuator 600 includes the pressure chamber 631 andthe rotary piston 620.

In some embodiments, the second piston can be oriented in the samerotational direction as the first piston. For example, the two pistons812 a and 822 a are oriented to operate cooperatively in the samerotational direction. In some embodiments, the second piston can beoriented in the opposite rotational direction as the first piston. Forexample, the rotary piston 610 is oriented to operate in the oppositerotational direction relative to the rotary piston 620.

In some implementations, rotating the rotary output shaft in a seconddirection opposite that of the first direction can include applyingpressurized fluid to the second pressure chamber, and urging the secondpiston partially outward from the second pressure chamber to urgerotation of the rotary output shaft in a second direction opposite fromthe first direction. For example, pressurized fluid can be applied tothe pressure chamber 631 to urge the rotary pistons 620 outward, causingthe rotor arm 640 to rotate counter-clockwise.

FIG. 13 is a perspective view of an example rotary piston actuator jointportion 1300 having modular support bands. In some embodiments, therotary piston actuator joint portion 1300 can be a modification of theexample rotary piston actuator joint portion 901 of FIG. 9 to include acollection of arcuate bearing sleeve assemblies 1350 a-1350 c (e.g.,modular support bands).

In some embodiments, the joint 1300 can be used with the multi-axisjoint 200 of FIG. 2, wherein the rotary piston actuator 400 has beenreplaced by a modular rotary piston actuator 900. In general, the joint1300 includes one or more rotary piston actuator modules, such as theexamples of the actuators 600, 700, and 800 discussed in thedescriptions of FIGS. 6A-8B.

The joint 1300 includes three rotary piston actuator modules 1302 a-1302c. Generally speaking, the rotary piston actuator modules 1302 a-1302 care individually replaceable and are generally interchangeable withinthe joint 1300. In some embodiments, each of the modules 1302 a-1302 ccan be an embodiment of any one of the rotary piston actuators 300, 400,600, 700, or 800 of FIGS. 3-8B, any one of the rotary piston actuatormodules 902 a-902 c of FIG. 9, or any other appropriate rotary pistonactuator, rotary vane actuator, or combinations thereof.

The rotary piston actuator modules 1302 a-1302 c each include a rotarypiston assembly 1310 (e.g., the rotary piston assemblies 310, 810, 820,the rotary pistons 610, 620, 710, 720, 910) and a housing (not shown)which also serves as a pressure chamber assembly (e.g., the pressurechamber 320, the pressure chamber assemblies 630, 730, 860, 920). Whilethe example joint 1300 includes three of the modules 1302 a-1302 c,other embodiments can include greater and/or lesser numbers ofcooperative and opposing rotary pistons actuator modules in variousconfigurations.

Each of the example rotary piston assemblies 1310 shown in FIG. 13,includes a rotary piston 1312 (e.g., the rotary piston 912). Each of therotary pistons 1312 includes a piston end 1316 and one or more connectorarms 1318. The piston ends 1316 are formed to have bodies having agenerally semi-circular arcs with substantially smooth surfaces.

The pressure chamber assemblies (e.g., the pressure chamber 320, thepressure chamber assemblies 630, 730, 860, 920) have a generallycylindrical shape. An outer housing 1341 (e.g., the outer housing 941)is configured as a tubular wall surrounding an interior bore sized toaccommodate the pressure chamber assemblies. In some embodiments, theouter housing 1341 can be connected to, or can be formed to be integralwith, a linkage such as the example linkage 980.

The outer housing 1341 substantially surrounds the pressure chamberassemblies. As the rotary pistons 1312 are actuated, the pressurechamber assemblies, which have a generally cylindrical shape, rotatewithin the outer housing 1341. The outer housing 1341 provides a bearingsurface that supports the pressure chamber assemblies as they rotate. Insome embodiments, contact between the pressure chamber assemblies andthe outer housing 1341 can bear a load. For example, a load on the jointarm 1364 can be transmitted to the pressure chamber assemblies, to theouter housing 1341 (e.g., through the bearing surface), and on to thelinkage.

The rotary piston actuator modules 1302 a-1302 c each include one of thearcuate bearing sleeve assemblies 1350, each formed as a modular wearband. Each of the arcuate bearing sleeve assemblies 1350 has a ringsection that is generally semicircular (e.g., crescent or “C” shaped).Each of the arcuate bearing sleeve assemblies 1350 is arranged radiallybetween the corresponding rotary piston 1312 and the inner wall of theouter housing 1341. The arcuate bearing sleeve assemblies 1350 are eachin contact with a radially outer side 1317 of a corresponding one of therotary pistons 1312 and the inner wall of the outer housing 1341. As therotary pistons 1312 are actuated, the arcuate bearing sleeve assemblies1350 each provide a bearing surface that contacts the radially outersides 1317 of the rotary pistons 1312 and supports the rotary pistons1312 as they extend and retract from the pressure chamber assemblies. Insome embodiments, contact between the rotary pistons 1312, the arcuatebearing sleeve assemblies 1350, and the outer housing 1341 can redirectradial loads on the rotary pistons 1312.

For example, as the rotary pistons 1312 extend, radial (e.g., outward)forces may develop. Such radial loads can place increased stress uponpiston seals (e.g., the seals 670, 672 of FIGS. 6A, 6B), causingincreased friction and wear, and increased friction and wear can reduceperformance (e.g., torque output) and lifespan (e.g., time to seal orother component failure). To reduce the effects of such radial forces,the arcuate bearing sleeve assemblies 1350 are contacted by the rotarypistons 1312 as the rotary pistons 1312 extend. Radial forces exerted bythe rotary pistons 1312 is transmitted through arcuate bearing sleeveassemblies 1350 to the to the housing 1341, thus providing a force thatresists and/or redirects the radial forces and at least partly relievesradial stresses placed upon the seals. As the stresses are relieved,actuator performance (e.g., torque) is maintained or restored.

FIG. 14 is an exploded view of an example arcuate bearing sleeveassembly 1400 for rotary piston actuators. In some embodiments, thearcuate bearing sleeve assembly 1400 can be one of the example arcuatebearing sleeve assemblies 1350 of FIG. 13 (e.g., a modular supportband).

The example arcuate bearing sleeve assembly 1400 includes an arcuatesupport portion 1410. The arcuate support portion 1410 includes a ringsection 1412 that is generally semicircular (e.g., crescent or “C”shaped). A mounting portion 1414 a extends radially outward from a firstend of the ring section 1412 at a first end, and mounting portion 1414 bextends radially outward from a second end of the ring section 1412. Themounting portions 1414 a-1414 b each have an arcuate outer surface 1416that is configured to substantially conform to the curvature of theinner wall of the outer housing 1341. The arcuate support portions 1410include a collection of apertures 1418 configured to accept a collectionof fasteners, for example, to removably affix the arcuate supportportions 1410 to the inner wall of the outer housing 1341.

The example arcuate bearing sleeve assembly 1400 also includes a linerportion 1450. The liner portion 1450 is generally semicircular (e.g.,crescent or “C” shaped), with a radially outer surface 1452 that isconfigured to conform to an inner surface 1420 of the arcuate supportportion 1410, and a radially inner surface 1454 that is configured toconform to the radially outer surface of the rotary pistons 1312. Theliner portion 1450 is semi-concentrically assembled to the arcuatesupport section 1410 such that the radially outer surface 1452 contactsthe inner surface 1420.

In some embodiments, the liner portion 1450 is a wearable member thatcan be replaced. For example, contact between the rotary piston 1312 andthe arcuate bearing sleeve portion 1400 over time can cause wear of theliner portion 1450. The liner portion 1450 can be removed and replacedto maintain the radial load bearing capability of the arcuate bearingsleeve assembly 1400.

In some embodiments, the liner portion 1450 can includefriction-reducing features. For example, the liner portion 1450 can beat least partly constructed or coated with friction-reducing materials(e.g., PTFE). In other examples, the inner surface 1454 can be textured(e.g., crosshatched) to retain and/or distribute lubricants to points ofcontact between the inner surface 1454 and the rotary pistons 1312.

FIGS. 15A and 15B are a sectional side view and exploded view,respectively, of another example rotary piston actuator 1500 having anarcuate bearing sleeve assembly. The actuator 1500 includes a rotarypiston assembly 1520 and a pressure chamber assembly 1530.

The rotary piston assembly 1520 includes a rotor shaft 1521. A rotor arm1522 extends radially from the rotor shaft 1521, the distal end of therotor arm 1522 including a bore 1556 substantially aligned with the axisof the rotor shaft 1521 and sized to accommodate a connector pin 1524.

The actuator includes a rotary piston 1550 that includes a piston end1552 and one or more connector arms 1554. The piston end 1552 is formedto have a generally semi-circular body having a substantially smoothsurface. Each of the connector arms 1554 includes a bore 1557substantially aligned with the axis of the semi-circular body of thepiston end 1552 and sized to accommodate the connector pin 1524.

The rotary piston 1550 may be assembled to the rotor shaft 1521 byaligning the connector arm 1554 with the rotor arms 1522 such that thebore 1556 of the rotor arm 1522 aligns with the bore 1557 of theconnector arm 1554. The connector pin 1524 may then be inserted throughthe aligned bores to create a hinged connection between the piston 1550and the rotor shaft 1521. The connector pin 1524 is slightly longer thanthe aligned bores. In the example assembly, about the circumferentialperiphery of each end of each connector pin 1524 that extends beyond thealigned bores is a circumferential recess (not shown) that canaccommodate a retaining fastener (not shown), e.g., a snap ring orspiral ring.

The rotary piston 1550 is inserted into a corresponding pressure chamber1510 formed as an arcuate cavity in the pressure chamber assembly 1530.The pressure chamber 1510 includes a seal assembly 1512 about theinterior surface of the pressure chamber 1510 at an open end 1513. Insome implementations, the seal assembly 1512 can be a circular orsemi-circular sealing geometry retained on all sides in a standard sealgroove. In some implementations, a commercially available reciprocatingpiston or cylinder type seal can be used. For example, commerciallyavailable seal types that may already be in use for linear hydraulicactuators flying on current aircraft may demonstrate sufficientcapability for linear load and position holding applications. In someimplementations, the sealing complexity of the actuator 1500 may bereduced by using a standard, e.g., commercially available,semi-circular, unidirectional seal design generally used in linearhydraulic actuators. In some embodiments, the seal assembly 1512 can bea one-piece seal.

In some embodiments of the example actuator 1500, the seal assembly 1512may be included as part of the rotary piston 1550. For example, the sealassembly 1512 may be located near the piston end 1552, opposite theconnector arm 1554, and slide along the interior surface of the pressurechamber 1510 to form a fluidic seal as the rotary piston 1550 moves inand out of the pressure chamber 1510. In some embodiments, the sealassembly 1512 can act as a bearing. For example, the seal assembly 1512may provide support for the piston 1550 as it moves in and out of thepressure chamber 1510.

In some embodiments, the actuator 1500 may include a wear member betweenthe piston 1550 and the pressure chamber 1510. For example, a wear ringmay be included in proximity to the seal assembly 1512. In anotherexample, the actuator 1500 may include one or more roller (e.g., needle)bearings in proximity to the seal assembly 1512. The wear ring and/orroller bearings may act as pilots for the piston 1512 and/or act asbearings providing support for the piston 1512.

In the example actuator 1500, when the rotary piston 1550 is insertedthrough the open end 1513, the seal assembly 1512 contacts the interiorsurface of the pressure chamber 1510 and the substantially smoothsurface of the piston end 1552 to form a substantially pressure-sealedregion within the pressure chamber 1510. The pressure chamber 1510 mayinclude a fluid port (not shown) formed through the pressure chamberassembly 1530, through which pressurized fluid may flow. Uponintroduction of pressurized fluid, e.g., hydraulic oil, water, air, gas,into the pressure chamber 1510, the pressure differential between theinterior of the pressure chamber 1510 and the ambient conditions outsidethe pressure chamber 1510 causes the piston end 1552 to be urged outwardfrom the pressure chamber 1510. As the piston end 1552 is urged outward,the piston 1550 urges the rotary piston assembly 1520 to rotate.

The example actuator 1500 includes an arcuate bearing sleeve assembly1580 that is removably affixed to the pressure chamber 1510. In someembodiments, the arcuate bearing sleeve assembly 1580 can be the examplearcuate bearing sleeve assembly 1400 of FIG. 14. As the piston 1550extends rotationally, the piston 1550 can also exhibit a radiallyoutward force. Without additional radial mechanical support, thisradially outward force could increase the amount of load that is exertedagainst the seal assembly 1512, which can increase friction and wear andreduce the performance (e.g., torque capacity) of the actuator 1500. Toreduce this effect, the arcuate bearing sleeve assembly 1580 providesradial mechanical support for the piston 1550.

The arcuate bearing sleeve assembly 1580 has an arcuate support portion1582 and a liner portion 1584. The liner portion 1584 is generallysemicircular (e.g., crescent or “C” shaped), with a radially outersurface 1585 that is configured to conform to an inner surface 1583 ofthe arcuate support portion 1582. The arcuate support portion 1582 isformed as a ring section that is generally semicircular (e.g., crescentor “C” shaped). A radially inner surface 1586 of the liner portion 1584is configured to conform to the radially outer surface 1551 of therotary piston 1550. The liner portion 1584 is semi-concentricallyassembled to the arcuate support section 1582 such that the radiallyouter surface 1551 contacts the inner surface 1586.

With the arcuate bearing sleeve assembly 1580 in place, as the piston1550 extends rotationally, a radially outer side 1551 of the pistoncontacts the liner portion 1584. Radially outward forces exhibited bythe rotary piston 1550 bring the rotary piston into contact with theliner portion 1584, which transmits the forces through the arcuatesupport portion 1582 to the pressure chamber assembly 1530. Theconnection between the pressure chamber assembly 1530 and the arcuatesupport portion 1582 causes the arcuate bearing sleeve assembly 1580 toresist (e.g., redirect, constrain) outward radial forces presented bythe rotary piston 1550. In some examples, the arcuate bearing sleeveassembly 1580 bears loads that would otherwise be borne by the sealassembly 1512, thereby maintaining the performance (e.g., torquecapability, seal life) of the rotary piston actuator 1500.

In some embodiments of the example actuator 1500, the pressure chamberassembly 1530 can be formed from a single, unitary piece of materialhaving no seams other than those created by the open end 1513 or thefluid port. For example, the pressure chamber 1510, the opening 1513,and the fluid port may be formed by molding, machining, or otherwiseforming a unitary piece of material.

FIG. 16 is a sectional side view of another example arcuate bearingsleeve assembly 1600. In some embodiments the arcuate bearing sleeveassembly 1600 can be all or part of the arcuate bearing sleeveassemblies 1350, 1400, and/or 1580 of FIGS. 13-15B. As discussedpreviously, arcuate bearing sleeve assemblies can includefriction-reducing features. For example, arcuate bearing sleeveassemblies can be constructed or coated with friction-reducing materials(e.g., PTFE) and/or can be textured (e.g., crosshatched) to retainand/or distribute lubricants to points of contact between the assemblyand the rotary pistons.

In the example of the arcuate bearing sleeve assembly 1600, a collectionof recirculating ball (or roller) bearings 1610 provide afriction-reducing feature that can constrain or redirect outward radialforces of the rotary piston 1550. The radially outer surface 1551 of therotary piston 1550 contacts a subset of the bearings 1610, and thebearings 1610 roll or spin as the rotary piston 1550 moves relative tothe arcuate bearing sleeve assembly 1600.

FIG. 17 is a sectional side view of another example arcuate bearingsleeve assembly 1700. In some embodiments, the arcuate bearing sleeveassembly 1700 can be all or part of the arcuate bearing sleeveassemblies 1350, 1400, and/or 1580 of FIGS. 13-15B. As discussedpreviously, arcuate bearing sleeve assemblies can includefriction-reducing features.

In the example of the arcuate bearing sleeve assembly 1700, a collectionof bearing assemblies 1710 provide a friction-reducing feature that canconstrain or redirect outward radial forces of a rotary piston 1701.Each bearing assembly 1710 includes a piston bearing 1712 and a housingbearing 1714. The piston bearing 1712 is arranged such that it will becontacted by the radially outer surface 1702 of the rotary piston 1701as the rotary piston 1701 extends and retracts (e.g., in and out of thepressure chamber assembly 1530). The housing bearing 1714 is arrangedsuch that it will contact both the piston bearing 1712 and a radiallyinner surface 1733 of an arcuate housing 1730.

In use, the rotary piston 1701 contacts the piston bearing 1712.Radially outward forces given by the rotary piston 1701 are transmittedto the piston bearing 1712, to the housing bearing 1714, and to theradially inner surface 1733 of the housing 1730. As such, the housing1730 can at least partly resist, constrain, and/or redirect the radiallyoutward forces of the rotary piston 1701.

In some embodiments, the rotary piston 1701 can be the example rotarypiston 1550 and the housing 1730 can be the example arcuate supportportion 1582. For example, the rotary piston 1550 can contact the pistonbearing 1612, and radially outward forces given by the rotary piston1550 are transmitted to the piston bearing 1712, to the housing bearing1714, and to the radially inner surface of the outer housing 1550. Assuch, the arcuate support portion 1582 can at least partly resist,constrain, and/or redirect the radially outward forces of the rotarypiston 1550.

In some embodiments, the rotary piston 1701 can be the example rotarypiston 1312 and the housing 1730 can be the example outer housing 1341.For example, the rotary piston 1312 can contact the piston bearing 1712,and radially outward forces given by the rotary piston 1312 aretransmitted to the piston bearing 1712, to the housing bearing 1714, andto the radially inner surface of the outer housing 1341. As such, theouter housing 1341 can at least partly resist, constrain, and/orredirect the radially outward forces of the rotary piston 1312.

In some embodiments, the piston bearing 1712 can have a larger orsmaller diameter than the housing bearing 1714. For example, in someembodiments the housing 1730 and the rotary piston 1701 may both move inthe same rotation direction, but not at the same speed. A difference indiameters between the piston bearing 1712 and the housing bearing 1714can provide a speed adaptation function (e.g., provide a gear reductionor amplification) between the rotary piston 1701 and the housing 1730.In the example of the rotary piston actuator joint portion 1300, boththe outer housing 1341 and the rotary piston 1312 move in the samedirection with similar angular velocities but with different linearvelocities. By having multiple bearings (e.g., the piston bearing 1712and the housing bearing 1714) in each of the bearing assemblies 1710,the rolling action of the bearings is made compatible with both themotion of the rotary piston 1701 and the housing 1730. Furthermore, byhaving the multiple bearings formed with the appropriate differentdiameters, the gearing action of the bearing assembly 1710 can make therolling action of the bearings compatible with both the motion of therotary piston 1701 and the housing 1730.

FIG. 18 is a flow diagram of an example process 1800 for performingrotary actuation of an example rotary piston actuator joint portionhaving arcuate bearing sleeve assemblies. In some implementations, theprocess 1800 may be used with systems having the example arcuate bearingsleeve assemblies 1350 of FIG. 13, the example arcuate bearing sleeveassembly 1400 of FIG. 14, the example arcuate bearing sleeve assembly1580 of FIGS. 15A-15B, the example arcuate bearing sleeve assembly 1600of FIG. 16, or the example arcuate bearing sleeve assembly 1700 of FIG.17.

At 1810 a first rotary actuator is provided. The rotary actuatorincludes a first housing defining first arcuate chamber including afirst cavity having a first open end, and an arcuate-shaped first pistondisposed in said first housing for reciprocal movement in the firstarcuate chamber through the first open end, wherein a first seal, thefirst cavity, and the first piston define a first pressure chamberincluding part or all of the first arcuate chamber, and a first arcuatebearing sleeve assembly having an inner surface configured to becontacted by a radially outer side of the first piston. For example, theexample joint 1300 includes the three rotary piston actuator modules1302 a-1302 c. The rotary piston actuator modules 1302 a-1302 c eachinclude one of the arcuate bearing sleeve portions 1350, placed radiallybetween the piston 1312 and the inner wall of the housing 1341.

At 1820, the first piston is urged partially rotationally outward fromthe first pressure chamber. For example, the piston 1312 of the rotarypiston actuator module 1302 a can be urged out of the pressure chamber(e.g., the pressure chamber 650 of FIGS. 6A-6B).

At 1830 a first radial force is applied by the first arcuate bearingsleeve assembly to the radially outer side of the piston. For example,as the rotary pistons 1312 extend, the radially outer sides 1317 contactthe arcuate bearing sleeve assemblies 1350. This contact can provide aradial force that constrains radially outward movement of the rotarypistons 1312.

In some implementations, the process 1800 can include urging the firstpiston partially radially outward, contacting the first piston to thefirst arcuate bearing sleeve assembly with a second radial force,transmitting the second radial force to the rotor assembly, andconstraining, by first arcuate bearing sleeve assembly, the secondradial force. For example, radially outward forces exhibited by therotary pistons 1312 can be transmitted to the housing 1341 through thearcuate bearing sleeve assemblies 1350. The housing 1341 constrainsthese forces, including the radial forces of the rotary pistons 1312.

In some implementations, the process 1800 can also include providing asecond rotary actuator, wherein the rotor assembly rotatably surroundsthe first rotary actuator and the second rotary actuator. For example,the rotary piston actuator module 1302 a can be assembled within thehousing 1341. The rotary piston actuator module 1302 b can also beassembled within the housing 1341, which rotatably surrounds both of therotary piston actuator modules 1302 a and 1302 b.

In some implementations, the process 1800 can also include redirectingthe first radial force through the first arcuate bearing sleeve assemblyto a rotor assembly rotatably surrounding said first housing anddefining a central bore within an inner wall of the rotor assembly,wherein the first arcuate bearing sleeve assembly is removably affixedto the first housing. For example, the radially outward forces exhibitedby the rotary pistons 1312 can be transmitted to the housing 1341through the arcuate bearing sleeve portions assemblies 1350. The housing1341 constrains these forces, including the radial forces of the rotarypistons 1312.

In some implementations, the first radial force can be redirectedthrough the first arcuate bearing sleeve assembly to the first housing,wherein the first arcuate bearing sleeve assembly is removably affixedto the first housing. For example, the arcuate bearing sleeve assembly1580 is removably affixed to the pressure chamber 1510.

In some implementations, applying by the first arcuate bearing sleeveportion a first radial force to the radially outer side of the pistoncan also include applying the first radial force to a collection ofbearings in contact with the radially outer side of the piston. Forexample, the radial forces of the rotary piston 1550 can be transmittedthough the collection of bearings 1610. In another example, the radialforces of the rotary piston 1701 can be transmitted through thecollection of bearing assemblies 1710.

Although a few implementations have been described in detail above,other modifications are possible. For example, the logic flows depictedin the figures do not require the particular order shown, or sequentialorder, to achieve desirable results. In addition, other steps may beprovided, or steps may be eliminated, from the described flows, andother components may be added to, or removed from, the describedsystems. In another example, various ones of the pistons can havesquare, rectangular, ovoid, elliptical, figure-eight, or circular shapesin cross-section. Accordingly, other implementations are within thescope of the following claims.

What is claimed is:
 1. A fluid actuator comprising: a housing comprising a first chamber wall defining an arcuate first chamber, a first fluid port in fluid communication with the arcuate first chamber, and a first open end; a first piston assembly comprising an arcuate-shaped tubular first piston comprising a second chamber wall defining an arcuate second chamber, a second fluid port in fluid communication with the arcuate second chamber, a enclosed end, and a second open end, disposed in said housing for reciprocal movement in the first chamber through the first open end relative to the housing, wherein a first seal, the first chamber wall, and the first piston define a first pressure chamber; and a second piston assembly comprising an arcuate-shaped second piston disposed in said first piston assembly for reciprocal movement in the second chamber through the second open end relative to the housing, wherein a second seal, the second chamber wall, and the second piston define a second pressure chamber, and a first portion of the second piston contacts a first end effector.
 2. The fluid actuator of claim 1, wherein: the housing further comprises a third arcuate chamber wall defining an arcuate third chamber, a third fluid port in fluid communication with the third chamber, and a third open end; the first piston assembly further comprises an arcuate-shaped tubular third piston comprising a fourth arcuate chamber wall defining an arcuate a fourth chamber, a fourth fluid port in fluid communication with the arcuate fourth chamber, and a fourth open end, disposed in said housing for reciprocal movement in the arcuate third chamber through the third open end relative to the housing, wherein a third seal, the third chamber wall, and the third piston define a third pressure chamber; and the second piston assembly further comprises an arcuate-shaped fourth piston disposed in said first piston assembly for reciprocal movement in the arcuate fourth chamber through the fourth open end relative to the housing, wherein a fourth seal, the fourth chamber wall, and the fourth piston define a fourth pressure chamber, and a first portion of the fourth piston contacts the first end effector.
 3. The fluid actuator of claim 2, wherein the third piston is configured to be actuated in the opposite rotational direction as the first piston.
 4. The fluid actuator of claim 2, wherein: application of pressurized fluid to the third pressure chamber urges the third piston partially outward from the third pressure chamber to urge rotation of the first piston assembly in a first direction; application of pressurized fluid to the fourth pressure chamber urges the fourth piston partially outward from the fourth pressure chamber to urge rotation of the second piston assembly in the first direction; rotation of the second piston assembly in a second direction opposite that of the first direction urges the fourth piston partially into the fourth pressure chamber to urge pressurized fluid out the fourth fluid port; and rotation of the first piston assembly in the second direction urges the third piston partially into the third pressure chamber to urge pressurized fluid out the third fluid port.
 5. The fluid actuator of claim 1, wherein the housing further defines an arcuate actuation space defining an actuation arc about the axis through the first open end, and the fluid actuator further comprises a rotor assembly comprising a rotary output tube rotatably surrounding said housing, wherein the rotor arm extends radially outward to the rotary output tube and the rotor arm is coupled to the rotary tube.
 6. The fluid actuator of claim 1, wherein the first seal is disposed about an interior surface of the first open end.
 7. The fluid actuator of claim 1, wherein the first seal is disposed about the periphery of the enclosed end, and is configured to remain stationary relative to the first piston and slide along the interior surface of the first pressure chamber as the first piston moves relative to the housing.
 8. The fluid actuator of claim 1, wherein the second seal is disposed about an interior surface of the second open end.
 9. The fluid actuator of claim 1, wherein the second seal is disposed about the periphery of the second piston and is configured to remain stationary relative to the second piston.
 10. The fluid actuator of claim 1, wherein the housing is formed as a one-piece housing.
 11. The fluid actuator of claim 1, wherein the first piston has one of a square, rectangular, ovoid, elliptical, figure-eight, or circular shape in cross-section.
 12. A method of fluid actuation comprising: providing a fluid actuator comprising: a housing comprising a first chamber wall defining an arcuate first chamber, a first fluid port in fluid communication with the arcuate first chamber, and a first open end; a first piston assembly comprising an arcuate-shaped tubular first piston comprising a second chamber wall defining an arcuate second chamber, a second fluid port in fluid communication with the arcuate second chamber, a enclosed end, and a second open end, disposed in said housing for reciprocal movement in the arcuate first chamber through the first open end, wherein a first seal, the arcuate first chamber, and the first piston define a first pressure chamber; and a second piston assembly comprising an arcuate-shaped second piston disposed in said first piston assembly for reciprocal movement in the arcuate second chamber through the second open end, wherein a second seal, the arcuate second chamber, and the second piston define a second pressure chamber, and a first portion of the second piston contacts an end effector; applying pressurized fluid to the first pressure chamber; urging the first piston partially outward from the first pressure chamber to urge the end effector in a first direction; urging the end effector in a second direction opposite that of the first direction; urging the first piston partially into the first pressure chamber to urge pressurized fluid out the first fluid port; applying pressurized fluid to the second pressure chamber; urging the second piston partially outward from the second pressure chamber to urge the second piston assembly in the first direction; urging the second piston assembly in the second direction; and urging the second piston partially into the second pressure chamber to urge pressurized fluid out the second fluid port.
 13. The method of claim 12, further comprising: urging the first piston partially outward from the first pressure chamber to urge the end effector in a first direction further comprises rotating the rotor arm in the first direction with substantially constant torque over stroke; and urging the second piston partially outward from the second pressure chamber to urge the first piston assembly in the first direction further comprises rotating the first piston assembly in the first direction with substantially constant torque over stroke.
 14. An arm of a machine apparatus comprising: a first arm portion; a second arm portion; and a joint portion connecting the first arm portion to the second arm portion, the joint portion comprising a fluid actuator comprising: a housing comprising a first chamber wall defining an arcuate first chamber, a first fluid port in fluid communication with the first arcuate chamber, and a first open end; a first piston assembly comprising an arcuate-shaped tubular first piston comprising a second chamber wall defining an arcuate second chamber, a second fluid port in fluid communication with the arcuate second chamber, a enclosed end, and a second open end, disposed in said housing for reciprocal movement in the first chamber through the first open end relative to the housing, wherein a first seal, the arcuate first chamber, and the first piston define a first pressure chamber; and a second piston assembly comprising an arcuate-shaped second piston disposed in said first piston assembly for reciprocal movement in the second chamber through the second open end relative to the housing, wherein a second seal, the arcuate second chamber, and the second piston define a second pressure chamber, and a first portion of the second piston contacts an end effector.
 15. The arm of claim 14, wherein the end effector is affixed to or is integral to the first arm portion.
 16. The arm of claim 14, wherein the housing is affixed to or is integral to the second arm portion. 